World heritage refers to the rare and irreplaceable wealth of mankind confirmed by UNESCO and the World Heritage Committee.It is a cultural relic and natural landscape with outstanding significance and universal value recognized by all mankind.In a narrow sense,the world heritage includes four categories:"world cultural heritage","world natural heritage","world cultural and natural heritage"and"cultural landscape".In a broad sense,according to the form and nature,world heritage is divided into cultural heritage,natural heritage,cultural and natural dual heritage,memory heritage,human oral and intangible heritage(intangible cultural heritage for short),cultural landscape heritage

In 1959,the Egyptian government planned to build the Aswan High Dam,which would have flooded valuable ancient sites in the Nile Valley,such as the Abu Simbel shrine.In 1960,UNESCO launched the Nubia Action Plan,and monuments such as the temples of Abu Simbel and Philae were carefully dismantled,transported to the highlands,and rebuilt piece by piece.More than 50 countries contributed more than$40 million of the$80 million conservation effort.The operation was considered so successful that it inspired other similar conservation efforts,such as the rescue of the water city of Venice in Italy,the ruins of Mohenjo-Daro in Pakistan,and Borobudur in Indonesia.Later,UNESCO and the International Council on Monuments and Sites drafted an agreement to protect the cultural heritage of mankind.

The United States was the first to join the convention,in 1973,and about 180 other countries joined.

In 1977,UNESCO's World Heritage Committee officially held a meeting to evaluate the world's cultural heritage.World cultural heritage includes:①cultural relics,②architectural complexes,③ruins.World natural heritage sites include:(1)natural features of geological and biological structures,(2)ecological areas of endangered flora and fauna,and(3)natural attractions.

In 1992,the 16th session of the World Heritage Committee of UNESCO proposed to include"cultural landscape heritage"in the World Heritage Catalogue,which specifically represents the common works of nature and human beings as stated in Article 1 of the Convention on the Protection of World Culture and Heritage.Cultural landscape heritage includes:(1)garden and park landscape,(2)organic evolution landscape(the material evidence of human historical evolution),(3)relevant cultural landscape.

In 1992,UNESCO launched the Memory of the World Documentary Heritage(also known as the Memory of the World Project or the Memory of the World Register),an extension of the world's cultural heritage,with the aim of rescuing and preserving documentary records to make human memory more complete.

In 1998,UNESCO adopted a resolution to establish the"Intangible Cultural Heritage"selection,in order to protect cultural diversity and stimulate creativity.This is a joint project with the Convention on the Protection of the World Cultural and Natural Heritage to protect the material cultural heritage,and is generally regarded as the integral content of the World Heritage.

In 1998,the Semerin Railway in Austria and the Darjeeling Himalayan Railway in India were added to the World Heritage List in 1999,extending a"linear cultural heritage"type with value for tourism development.

In 2002,the United Nations Food and Agriculture Organization(FAO),UNDP and the Global Environment Facility(GEF)established the Global Important Agricultural Heritage Project(GIAHS).

In 2009,the Wetlands International Alliance launched the"Wetland Heritage"project to incorporate international wetlands into the World Heritage Conservation Strategy.