The Preservation of 20-Century Architectural Heritage in China: Evolution and Prospects

This article examines the fundamental meaning of 20-century architectural heritage by reviewing the formation of the concept by the International Council on Monuments and Sites (ICOMOS). It analyses the current state of conservation and potential threats to China’s built heritage, built environment, and cultural landscapes that are less than 50 years old. The article presents a thorough review of the facilitating process of the regulative infrastructure of Chinese modern architecture conservation. It makes a comparative study of several cities’ urban heritage assessment criteria as well as the first and second inventories of China’s 20-century architectural heritage. The article argues that conserving China’s 20-century heritage calls for a theoretical framework, which integrates value assessment and advancing the conservation mechanism for built heritage. In doing so, the transition may be facilitated from focusing on World Heritage towards heritage of the everyday, which embodies collective memories, and from preserving iconic monuments towards comprehensively conserving the built heritage.


Development of 20 th -Century Heritage
Since the beginning of the 21st century, cultural heritage conservation has been a worldwide movement and emerging creative activity. However, until the 1960s, conservation has focused on monuments and sites that date from prehistoric times until the mid-19th century. Rarely have sites after the Industrial Revolution-especially 20thcentury ones-appeared on the World Heritage List of International Council on Monuments and Sites (UNESCO). Since the 1970s, the scope of conservation subjects has been expanded to include historic houses, vernacular architecture, industrial buildings, and historic environments (such as traditional neighbourhoods and historic areas) for comprehensive conservation.
In October 1981, during the fifth session of the World Heritage Committee, the discussion about whether to include Sydney Opera House and Sydney Harbour on the World Heritage List caught the attention of ICOMOS regarding the conservation of post-war architecture and recent heritage. In several related international conferences that followed, the identification, assessment, listing, and conservation of recent heritage were discussed. In 1985, the conservation issues of modern heritage were first explored at the Advisory and Executive Committee and Bureau Meeting of ICOMOS. In 1988, the International Working-Party for Documentation and Conservation of Buildings, Sites and Neighbourhoods of the Modern Movement (DOCOMOMO) was established in Eindhoven, Netherlands.
In 1989, the Council of Europe organised an international colloquy titled '20 th -Century Architectural Heritage: Strategies for its Preservation and Promotion' in Vienna. In 1991, the Council of Europe published the 'Recommendation on the Protection of the 20th-Century Architectural Heritage' . That publication was centred on the idea of 'heritage as historical memories' , and it called for systematic inventories to be made that should include 20th-century heritage as much as possible; it also called for establishing conservation strategies based on heritage values. In 1995, the International Conference on Preserving the Recent Past was organised in Chicago. The conference promoted the active conservation of the cultural heritage of the recent past; it encouraged the most appropriate use and reuse of the architectural heritage of the recent past by considering it as cultural capital and a landscape resource.
Two ICOMOS seminars on 20th-century heritage were held in Helsinki in 1995(ICOMOS, 1995 and Mexico City in 1996. During the 12th general assembly of ICOMOS in 1999 in Mexico, several countries (Israel and some Eastern European nations) submitted their resolutions regarding the conservation of 'modern' heritage. In the 'Heritage at Risk 2000' report and subsequent reports, many countries raised their concern over the fate of late-19th-and 20th-century heritage. Following such concerns, an ICOMOS symposium was held in Montreal in September 2001, and the Montreal Plan for 20th-Century Heritage was developed (ICOMOS, 2001). At the same time, 18 April 2002 was chosen as the International Day for Monuments and Sites with respect to 20th-century heritage ( Figure 1).
In 2005, at the ICOMOS assembly in Xi'an, China, the ICOMOS International Scientific Committee for 20th-Century Heritage (ISC 20C) was established. In 2008, ISC 20C initiated the drafting of a comprehensive thematic 1 research report, supported by the Getty Conservation Institute. That report has contributed to raising awareness of modern heritage values and guiding various countries and territories in assessing and protecting such values. The report has also encouraged those places to include more modern heritage sites on proposed lists of World Heritage Sites and to prioritise the protection of ones in danger.
In June 2011, ISC 20C held an international conference called Intervention Approaches for the 20th-Century Architectural Heritage in Madrid. The conference adopted the ' Approaches for the Conservation of 20th-Century Architectural Heritage, Madrid Document 2011' , which has since been widely circulated and discussed (ICOMOS-ISC20C 2011). The second version of that document was published in 2014 by ISC 20C based on comments and discussions collected between 2011 and 2014. The Madrid document provides guidance for the conservation and management of 20th-century heritage. In December 2017, the third edition of the Madrid document was adopted during the ICOMOS 19th general assembly in Delhi. That third edition was renamed ' Approaches to the Conservation of 20th-Century Cultural Heritage. Madrid-New Delhi Document 2017 ' . There were some significant changes and amendments, such as the addition of 'provides policies to retain and respect' cultural significance (Article 2-2.3) and 'Recognise when use contributes to significance and manage accordingly' (Article 8); there were also several entries regarding the conservation requirements for cultural and historic urban landscapes (ICOMOS-ISC20C 2017).

Enlightenment regarding 20 th -Century Heritage
We are in an age when the definition of 'heritage' is being extended from meaning simply archaeological ruins, monuments, historic remains, architectural heritage, and urban heritage to including such matters as the concept of cultural heritage, cultural landscape, industrial heritage, and intangible cultural heritage. The quantity and categories of heritage are both increasing. The emerging notion of 20th-century heritage is closely related to preserving the history of the recent past. The heritage of the recent past was discussed at the Chicago conference entitled 'Preserving the Recent Past' in 1995; however, that referred only to the heritage for the 1920s-1960s. Today, the relevant international organisations and institutions have realised that recent heritage (especially modernist architectural heritage) constitutes a significant part of the common heritage of humankind. It is the straightforward manifestation of the evolution of architecture and society. 'Recent past' has become a standard technical term referring to heritage assets and built heritage that are less than 50 years old. 20th-century heritage includes the following: buildings of all styles and functions (new construction, vernacular architecture, reused buildings); urban ensembles (neighbourhoods, new towns); city parks, gardens, and landscapes; artwork, furniture, interiors, integrated industrial design; engineering works (roads, bridges, waterworks, harbours, industrial complexes); and archaeological or commemorative sites.
The application of pioneering technologies and materials in modern architecture usually implies the potential of unanticipated risks and issues, such as the rapid deterioration of lightweight concrete domes, synthetic materials, and large glass panes. Both iconic architectural works and ordinary buildings are liable to fall into decay or face the threat of demolition. Consequently, modern architecture is referred to as 'heritage at high risk' by experts from DOCOMOMO International, such as Maristella Casciato (Casciato and d'Orgeix 2007).
The concept of 20th-century heritage was established to address the fact that architecture from that period does not receive adequate acknowledgement and protectionespecially compared with older or conventional types of heritage. The works of the recent past do not seem to be as precious as ancient or high-profile monuments. The difference may be due to the relatively large amount of recent heritage, which creates challenges in selecting what to protect; it could also be the result of negative impressions, whereby modern constructions may be responsible for destroying the natural environment or historic sites.
Since the beginning of the 21st century, it has been widely recognised that 20th-century cultural heritage is part of human heritage and deserves proper conservation. Many buildings created through the Modern Movement have historical and cultural value; they demand care and protection so that they may be inherited by future generations . The architectural heritage of the Modern Movement is under great threat owing to the following: the life expectancy of the buildings; frequent technical innovations; the discrepancy between original functions and contemporary needs; and misleading aspects of cultural perceptions. Therefore, identifying and assessing the 20th-century heritage has to be conducted within a framework of sustainable development; that process should take into account the connection between the heritage and contemporary and future life. An evaluation of heritage projects should consider community expectations and pay particular attention to environmental, economic, and cultural activities.
In recent years, increasing numbers of 20th-century architectural heritage properties have appeared on the World Heritage List. In June 2007, the Sydney Opera House (completed in 1973) was inscribed at the 31st session of the World Heritage Committee in Christchurch, New Zealand as an outstanding example of 20th-century architecture ( Figure 2). In July 2008, Berlin Modernism Housing Estates were inscribed at the 32nd session of the World Heritage Committee. On 17 July 2016 at the World Heritage Committee Session held in Istanbul, the architectural work of Le Corbusier was inscribed as a serial property: it includes 17 buildings in seven countries (Argentina, Belgium, France, Germany, India, Japan, and Switzerland). Such actions by the international community are the best demonstration of the development of 20th-century architectural heritage conservation (Figure 3).
Considering the great number and wide distribution of 20th-century heritage properties, extensive social and  community participation is essential in sustaining their original functions or for their adaptive reuse. On the one hand, familiar landmarks can help communities in cities stay connected with their collective memories in a fastchanging world. The historic environment is as important as the natural environment and demands protection during urban development. Within the historic environment, urban architecture, vernacular architecture, and historic districts have been recognised as significant components of local symbolic landscapes and township characteristics. On the other hand, 20th-century heritage is relatively recent and has suffered less corrosion from the forces of nature. Thus far, most 20th-century heritage has retained its vitality. Hence, it is critical now that people from all walks of society should participate in conservation efforts. The Architecture Society of Japan has organised a specific committee for investigating, assessing, and conserving modern architecture. Representative architectural works by such eminent architects as Kunio Maekawa and Kenzo Tange have been listed in inventories of Japan's Registered Monuments and Designated Tangible Cultural Properties (Figures 4, Figures 5). In December 2017, ICOMOS Japan selected a list of 20 Japanese 20th-century heritage projects, such as Yoyogi National Gymnasium (Tokyo), the Great Seto Bridge (Kagawa), and the Tokaido Shinkansen (Tokyo-Osaka).
In April 2008, in line with trends in international heritage conservation, the Wuxi Forum on the Conservation of China's Cultural Heritage with the theme of '20thcentury heritage conservation' was held in Wuxi. At the forum, the Wuxi recommendation for 20th-century heritage conservation was discussed and adopted ( Figure 6). In May that year, the State Administration of Cultural Heritage (SACH) announced the 'Notice regarding Enhancing the Conservation of 20th-Century Architectural Heritage'; that notice called for sufficient attention to rescue and conserve China's 20th-century heritage. Since then, 20th-century heritage has been a heated topic in the country's media.

Conservation of Modern Heritage in China: Legislation Development
Together with China's Ministry of Culture, the Ministry of Urban and Rural Construction and Environmental Protection published the 'Notice regarding the Emphasis on Surveying and Preserving Modern Architecture' in November 1988. Since then, investigations on modern architecture to various extents have been conducted across the country. Following the principle of that notice, Shanghai began conducting surveys and assessments of modern architecture in 1989. In 1991, Shanghai was China's first city to establish local-level regulations for the conservation of outstanding modern architecture: Conservation and Management Regulations for the Outstanding Modern Architecture in Shanghai. At the same time, the municipality published the first inventory of 61 listed outstanding modern buildings.
In July 1991, in the 'Notice regarding Publishing the Summary of the Evaluation Meeting for Outstanding Modern Buildings' , the Ministry of Housing and Urban-Rural Development (MOHURD) and SACH called for general surveys and the listing of valuable buildings as local-level Protected Cultural Heritage Sites (PCHS). In November 1996, after assessment and publication of the fourth inventory of National PCHS, that categorisation was adopted. The category of 'revolutionary ruins and   (1982), one category of cultural heritage that falls under state protection is 'buildings, memorial sites and memorial objects related to major historic events, revolutionary movements or famous people that are highly memorable or are of great significance for education or for the preservation of historical data' . It is evident that the legislation for heritage conservation focuses on the memorial, educational, and political significance of historic buildings. In 2003, MOHURD formulated the Measures for the Administration of City Purple Lines; those measures required municipal governments to define 'purple lines' when drafting conservation plans to protect Famous Historic and Cultural Cities (FHCC). A purple line is a demarcation line: it defines the area of protection for historic districts and buildings. In 2004, MOHURD released the ' Advice regarding Enhancing the Conservation Planning of Outstanding Modern and Contemporary Urban Architecture' (hereafter, 'the Advice'); the Advice requested greater effort in conserving the heritage of modern urban buildings. The objects of protection include buildings with high historic and cultural value constructed from the mid-19th century to the 1950s. The Advice required that local governments actively advance the legislative process for special laws, conservation planning of modern and contemporary buildings, and strict implementation of conservation measures in conservation plans. In August 2004, the Architect Branch of the Architecture Society of China, led by Guoxin Ma, submitted the List of Chinese 20th-Century Architectural Heritage to the International Union of Architects; the list called for attention to modern and contemporary architecture in need of urgent rescue or under threat of destruction (Shan 2008).
The Regulation on the Protection of Famous Historic and Cultural Cities, Towns and Villages was implemented on 1 July 2008; it explicitly requires local governments to protect historic buildings across the country. The term 'historic building' here refers to 'a building or structure which has certain value for protection and can reflect historical features and local characteristics' (Article 47). The regulation requires that municipal governments protect historic buildings that are not included in the PCHS system; it specifies the management and conservation requirements regarding financial resources, control of demolition, and construction. The regulation provides legislative support for local governments to protect heritage buildings. To some extent, the regulation has reduced the unfortunate large-scale demolition of historic buildings that lack PCHS status through not having been considered legally protected objects.
In September 2017, MOHURD released 'Notice regarding Enhancing the Conservation and Utilisation of Historic Buildings' . That notice required local governments to protect and make use of historic buildings; it called for efforts towards identifying, inventorying and documenting historic buildings so as to make the best use of their value.

Identification Criteria of Historic Buildings in Chinese Cities
Since 2000, before national regulations were implemented, such municipalities as Shanghai, Harbin, Xiamen, and Suzhou formulated specific conservation regulations for historic buildings and districts. The regulations were drafted in consideration of the municipalities' historic building types as well as local social and economic characteristics; the regulations referred to the more advanced conservation experience with the listed buildings protection system that applied for historic buildings in other countries. Such cities as Beijing and Nanjing adopted their own regulations about protection as FHCCs, and they included historic buildings for conservation.
Cultural heritage is clearly related to history: it is something we inherit from our predecessors and pass on to future generations. Cultural heritage includes cultural traditions and artificial products. Hence, the notion of age seems to be-at least implicitly-the primary evaluation indicator in all assessment criteria for cultural heritage. This section of the article presents a comparative analysis of the age criterion for the listing of historic buildings with respect to local conservation legislation and regulations of several Chinese cities.
The Regulation for the Protection of the Historic and Cultural City of Beijing , which went into effect on 1 May 2005, explicitly states the following: 'Courtyards and other buildings that have not been identified as immovable cultural heritage sites, that carry certain features of a time, that are of protection value, and that are carriers of authentic and comparatively complete historical information should be identified as architecture with protection value' (Article 14); 'it is prohibited to illegally demolish, reconstruct or expand architecture with protection value' (Article 31). Under this regulation, there are no explicit requirements regarding construction or completion dates of buildings. Among the criteria for conservation regulations in other cities, there are four relating to age: (1) before 1949; (2) over 50 years since completion; (3) over 30 years since completion; and (4) no specific requirements (Table 1).
It is notable that in 2013, both Wuhan and Hangzhou revised their previous conservation measures: they upgraded them from administrative operative measures to local-level conservation regulations. Regarding age criteria, Hangzhou changed the original standard of 'over 50 years since completion' to 'no specific requirements'; Wuhan changed the original standard of 'over 30 years since completion' to 'over 50 years since completion' .
For an extended period in the field of historic preservation in China, buildings aged under 50 years were not protected. Through this circumstance, many valuable buildings were demolished or are facing demolition. There are still no universal assessment criteria for 20thcentury heritage; however, consensus regarding the most relevant questions was reached in the 1995 ICOMOS seminar in Helsinki. The Helsinki seminar attempted to establish a methodology to identify 20th-century heritage sites that embody Outstanding Universal Values and evaluate whether such sites have potential for inclusion on the World Heritage List. The seminar concluded that the 20th-century heritage should be considered in terms of various factors, reflecting both the evolution and innovation of that century and traditional discourse and expression . It was agreed at the seminar that 'it would be advisable only in exceptional cases to propose for inclusion in the World Heritage List properties that are less than 25 years old in order to allow sufficient time for historical perspective and scientific analysis' (ICOMOS 1995). In other words, ICOMOS welcomed proposals for buildings or built environments older than 25 years for inclusion on the World Heritage List. When assessing and identifying heritage buildings and listed historic buildings, there is a tendency to pay greater attention to the age of construction and simply assume that the older the building, the more valuable it is. It is a misunderstanding of the World Heritage Convention that World Heritage nominations have to be masterpieces with a long history. The Madrid-New Delhi Document 2017 provided some specific guidance about how to 'identify and assess cultural significance' (Article 1) (ICOMOS-ISC20C 2017).

Current Situation for Listing 20 th -Century Heritage in China
As noted in the Wuxi recommendation for 20th-century heritage conservation, such conservation has already received professional attention but not sufficiently enough. The state of conservation of China's buildings from the recent past is far from good. Much significant 20th-century heritage is disappearing at a rapid rate owing to limitations of listing criteria, lack of legislative support and conservation experience and inappropriate utilisation. Rescuing and preserving these buildings has become a pressing issue. Some Historic and Cultural Cities are doing their best to preserve the architecture and landscapes of the past. Their historic buildings and cultural landscapes may not be unique treasures or have a distinctive historic legacy; however, their active conservation increases the charm of the cities and cultural identity of their citizens (Figure 7). Some proactive efforts have been undertaken in such cities as Shanghai, Suzhou, and Beijing. For example, in July 2002, the Municipal People's Congress of Shanghai adopted the Regulation of Shanghai Municipality on the Protection of Areas with Historical and Cultural Features and Outstanding Historic Buildings ; that regulation revised the term 'outstanding modern building' to 'outstanding historic building' . The age criterion of listed buildings was also changed from the original 'before 1949' to 'over 30 years since completion' . Since 1989, 1,058 entries, which  amount to 3,075 outstanding historic buildings, have been listed over five inventories. While protecting the numerous PCHS at multiple levels, Suzhou Municipality ensures the effective protection of historic buildings and structures related to historical features of its old town through local legislation and detailed control plans. There are 1,347 listed buildings in the old town (Table 2).
In December 2007, Beijing Municipality published the first inventory of the city's outstanding modern architecture. Among the 71 listed buildings, 51 (72%) were constructed after the founding of the People's Republic of China. Those listed modern buildings include the former Soviet Union Exhibition Hall (built in the 1950s), the 798 Factory Complex (Figure 8), Beijing Long-Distance Telephone Edifice (built in the 1970s), Beijing International Club, and diplomat apartments on Jianguomenwai Avenue. That was a promising start. However, many modern heritage sites across the country remain and include the following: post-1949 architecture; workers' new villages; public spaces and landscapes that appeared during the 10 years of the Cultural Revolution ( Figures  9, Figures 10); vernacular heritage ( Figure 11); industrial heritage; technological heritage; and classic architecture of the 1980s. There is an urgent need for extensive surveys, listing, and rescue.
A legal inventory specifically for China's 20th-century architectural heritage has yet to be compiled. In September 2016 and December 2017, the Chinese Society of Cultural Relics (CSCR) and the Architectural Society of China jointly released the first and the second inventories of Chinese 20th-Century Architectural Heritage (Jin, 2017). The heritage sites selected in the inventories were based on a vote among recommendations made by the 20th-Century Architectural Heritage Committee of CSCR (CSCR-C20C) and architects. Such an inventory created by academic institutes and professionals does not provide heritage sites with legally protected status or relevant legislative or policy support; however, it has raised widespread attention in society. Publication of the inventories has been beneficial in raising public awareness with respect to understanding architectural heritage and encouraging local governments to increase their conservation and management efforts.
The listing criteria and procedures of the above inventories are based on the Chinese 20th-Century Architectural Heritage Listing Criteria of 2014 (hereafter, 'Listing Criteria') established by the CSCR-C20C. The Listing Criteria are founded on the selection criteria for World Heritage Sites. The Listing Criteria state the following about a listed site: it should 'represent a masterpiece of human creative genius; demonstrate outstanding impact; bear a unique or at least exceptional testimony to a cultural tradition or to a civilization; be an outstanding example of work which illustrates (a) significant stage(s) in human history; be residential architecture with historical and cultural features; or be architecture associated with traditions or beliefs' . There are nine more specifics, detailed criteria listed in the document, including the following: 'to be an outstanding example of demonstrating Chinese urban  Gates with brick carvings 37 Table 2 Types and Quantity of protected buildings in the old town of Suzhou (Source: the author).  Figure 9 Hongtaiyang Square in Lijiang city (Cultural Revolution Landscape) (Source: the author). Figure 10 Cliff carvings from Cultural Revolution on the Jiangxin Island in Wenzhou city (Source: the author). Figure 11 The vernacular heritage in Qujiawan old town in Honghu city, Hubei Province (Source: the author).
spirit, to bear a significant testimony to the construction history of modern Chinese cities and significant historical events'; 'to be the carrier of the memories of urban historical cultural landscape, the architectural ruins and monuments associated with the modern history of China and significant events' , but also including 'historical testimony of less important eras which constitutes the integrity of architectural heritage' . From the perspective of the conservation mechanism, the two inventories have considerable overlap with the PCHS of various levels: 59.1% of the items in the inventories are National PCHS. Among the 98 listed buildings in the first inventory are 45 (45.3%) National PCHS; among the 100 listed buildings in the second inventory are 72 (72%) National PCHS. However, since the fourth inventory of National PCHS (which brought attention to the protection of outstanding modern architecture) and especially since the sixth and seventh inventories, the number of listed modern architectural heritage sites has increased considerably. The inventories of Chinese 20th-Century Architectural Heritage indicate the growing awareness of modern heritage conservation in the selection process of National PCHS (Figure 12).
In terms of geographical distribution, the listed sites are mostly concentrated in such cities as Beijing, Shanghai, and Nanjing; there is little balance across regions. Among the 198 heritage sites listed in the two inventories, 50 are in Beijing (25.3%), 24 in Jiangsu Province (12%), and 19 in Shanghai (10%) (Figures 13, Figures 14). This situation reflects the privileged political and economic status of the metropolis in recent history; it also underlines the emphasis on conserving modern architecture in the last three decades. Those figures indicate that there is greater need to focus attention on conserving historic buildings in medium-sized and small cities. The CSCR-C20C was aware of the imbalanced geographical distribution of listed buildings in the inventories. Hence, a public ceremony for the release of the second inventory in December 2017 was held in Chizhou, a city in Anhui Province. That ceremony operated as a catalyst for the city-branding scheme called 'Cultural Chizhou' . The selection process for the third inventory has started. Besides paying greater attention to geographical distribution, the selection committee has also made adjustments to the age criteria for buildings. The following statement appears in the Listing Criteria: 'Chinese 20thcentury architectural heritage is a collection of heritage that can be divided by time periods. The collection includes various types of architectural heritage that emerged during the historical evolution of the 20th century.' This statement also appears: 'There are mainly two historical time periods: modern Chinese architecture  and contemporary Chinese architecture (1949 to the early to mid-21st century). ' Those periods begin 60 years before the start of the 20th century and continue almost 20 years beyond the present. The aim with the Listing Criteria is to extend the listing of architectural heritage towards promoting architectural culture. It is not necessarily beneficial that local governments should be encouraged to focus on preserving the recent heritage. Educating all people about architecture is a necessity; however, in China, it is even more imperative for the government to carry out rescue and protection efforts for endangered architectural heritage . The items listed in protection lists should be weighted more towards local cities and villages. It is important for more attention to be paid to historic built environments facing destruction or demolition.
In view of the above observations, it is necessary to include in the Chinese 20th-Century Architectural Heritage inventory more buildings and structures aged 30-50 years. At a national level, there is a need for further protection of post-1949 architectural heritage that is associated with significant historic events and economic development, focusing specially in a time limit that can be extended to 10 to 20 years after the Reform and Opening-up of 1978 (gaigekaifang). Therefore, considering the types and 13 14 12 Figure 13 Geographical distribution of the 20 th -century architectural heritage in the first inventory (Source: the author). Figure 14 Geographical distribution of the 20 th -century architectural heritage in the second inventory (Source: the author).

Time Periods
Historical Characteristics

From World Heritage to Everyday Heritage
In recent years, China has paid more attention to cultural heritage; however, 'ancient' structures still tend to assume greater prominence. There has always been such a discrepancy in the value related to cultural heritage conservation in China, as expressed in the following quotations: 'emphasising the ancient but neglecting the recent'; 'understanding only prominent monuments, not minor ones'; 'destroying material remains to meet human needs'; and 'desiring the fake while devaluing the authentic' (Yang, 1998, 162-163). There exists a considerable amount of surviving 20th-century built heritage in China; however, owing to limited public understanding and self-interest tendencies, there is a pressing threat to those structures in the face of urban development (Figures 15, Figures 16).
The Recommendation Concerning the Preservation of Cultural Property Endangered by Public or Private Works adopted by UNESCO in 1968 explicitly states the following: 'the term "cultural property" includes not only the established and scheduled architectural, archaeological and historic sites and structure, but also the unscheduled or unclassified vestiges of the past as well as artistically or historically important recent sites and structures' (UNESCO 1968, 2). The Washington Charter (Charter for the Conservation of Historic Towns and Urban Areas), adopted by ICOMOS in 1987 also states that 'cultural properties, however modest in scale … constitute the 15 16

Figure 15
The demolished teaching building built in the 1950s designed by Jizhong Feng from Tongji University (Source: the author). Figure 16 Demolished high-rise residential building built in the 1980s designed by Fudong Dai from Tongji University (Source: the author).  memory of mankind' . That charter encourages seeking to promote the harmony of both private and community life in such areas and preserving their cultural properties (ICOMOS 1987, 1). The paradigm shift with cultural heritage constitutes a shift from the ancient to the recent, from classic to common objects. In this sense, the conservation movement is also transitioning from a focus on world heritage to the heritage of the everyday. That was clarified by former Cultural Advisor of UNESCO Asia-Pacific Richard Engelhardt as below (Table 4).

Epilogue: Way Forward
The history of the development of human society has always been filled with changes and challenges; the cycles of those changes seem to have become ever shorter and the pace ever faster. During that rapid evolution, we are in danger of losing the stable temporal-spatial feeling that is essential to our survival. We are losing the consistent relationships between one another as well as the connection between people and the materials around us. Jean Baudrillard describes this in The Consumer Society: Myths and Structures, We live by object time: by this I mean that we live at the pace of objects, live to the rhythm of their ceaseless succession. Today, it is we who watch them as they are born, grow to maturity and die, whereas in all previous civilizations it was timeless objects, instruments or monuments which outlived the generations of human beings. (Baudrillard 1998, 25) Internationally speaking, the methodology for the conservation of early 20th-century heritage has become quite comprehensive, whereas that for the post-war built heritage, it is essential to learn from the international experience and techniques. However, to construct a comprehensive theoretical system for conservation, it is also necessary to actively encourage interdisciplinary collaboration regarding academic research, value assessment, and conservation technology based on the specific characteristics of China's 20th-century heritage. Much improvement is needed for such aspects as institutional development, general surveys and research, conservation and restoration techniques, public participation, economic policy, and management planning. It is advisable to promote the creation of more non-governmental organisations; the general public should be encouraged to participate in conservation activities related to architectural heritage, and it is necessary to raise awareness among the general public about 20th-century architectural heritage conservation.
The trend for World Heritage nomination has grown stronger in China. That country now has the second-highest number of World Heritage Sites in the world, but no 20th-century heritage properties are listed among them. Hence, it would be prudent for China to refer to the assessment criteria and categorisation for World Heritage inscription: the value assessment of architectural heritage should take into account the respect for cultural diversity and culturally sustainable development. Towards improving the comprehensiveness and integrity of heritage assets, various types of 20th-century heritage properties in China, including architectural heritage, cultural landscapes, and vernacular architecture, deserve to be incorporated in the PCHS list or Historic Building Inventory. It is necessary to consider the association between historic events and monuments, the memorial and educational connotations of historical figures' former residences, and the memorial sites of 'Red Memory' . However, it is also necessary to analyse, research, identify, and assess the 20th-century architectural heritage from various perspectives, such as architecture, architectural anthropology, and architectural cultural transmission. It is desirable to list more historic buildings, the built environment heritage, and cultural and historic urban landscapes that are less than 50 years old in the cultural heritage inventory.
In terms of conserving, managing, and revitalising the 20th-century architectural heritage, strategic conservation plans need to address the issues of safeguarding the characteristics of a place, improving the quality of its environment, and planning and creating liveable habitats. In doing so, the attractiveness of cities and communities may be augmented and the identity of their citizens strengthened. Historical and cultural resources are significant assets for sustainable tourism development and urban innovation, which would be of benefit in the process of achieving urban development goals with high quality and liveability. As the president of ICOMOS ISC20C, Sheridan Burke, has pointed out, the thematic historical framework for 20th-century heritage prepared by the Getty Conservation Institute and ICOMOS ISC20C will be able to assist in conserving, managing, revitalising, and adaptively reusing the 20th-century architectural heritage (Burke, 2017). It is rational to believe that further implementation and standardisation of modern architecture conservation will encourage a more comprehensive assessment and more efficient management and utilisation of 20th-century heritage. (Translated by Lui Tam, proofread by Yingchun Li and Plácido González Martínez)