THE sites range from an 8,000-year-old city in Pakistan to the Statue of Liberty in New York Harbor, now almost a century old. Some, like Wadi Hadramaout in the People's Democratic Republic of Yemen, are little known beyond their own borders. Others, like India's Taj Mahal, are known throughout the world.
Some will draw tourists by the thousands. Others will appeal only to a handful of archaeologists.
But all of them are ''monuments'' to mankind's culture and creativity - and are increasingly the subject of major efforts at reconstruction and preservation.
Today is ''World Heritage Day,'' an observance date designated by the International Council on Monuments and Sites (ICOMOS). This nongovernmental alliance of national committees in 73 countries is committed to studying and conserving historic monuments, sites, buildings, and districts. The council also tries to cultivate people's interest in the protection of their own cultural heritage.
Such preservation is ''our shared responsibility,'' said Amadou-Mahtar M'Bow, director general of the United Nations Education, Scientific, and Cultural Organization (UNESCO), in an address before a preservation conference in Washington. ''As a result of the rapid changes which mark our time and of a greater opening out to the rest of the world,'' he said, ''man feels the need to leave his imprint upon time, and to preserve for himself and for his children the most representative testimony of his creative genius.''
World Heritage Day has been endorsed by UNESCO. Its promoters hope that by 1985 the observance will be reinforced in the United States by a presidential proclamation.
Meanwhile, the US committee on monuments and sites is observing the day with a detailed look at the restoration of the Statue of Liberty, which was recently nominated to join the World Heritage List. A campaign to raise $230 million has been launched by the Statue of Liberty-Ellis Island Foundation to refurbish the twin monuments to America's image as a haven for the world's homeless.
The 165 sites on the World Heritage List, all considered of ''universal value to mankind,'' include the Giza pyramids of Egypt, Chartres Cathedral and the Palace of Versailles in France, the Medina of Fez in Morocco, the city of Cuzco in Peru, Persepolis in Iran, the Katmandu Valley in Nepal, and the Old city of Jerusalem and its walls.
The deterioration or disappearance of these sites would be considered a ''harmful impoverishment to the heritage of all nations,'' according to ICOMOS statements.
The preservation ethic has flourished since World War II, with the growing pride of third-world nations in their own cultural, historic, and artistic monuments and traditions. Also, millions of people have become aware of the inexorable advance of bulldozers and wrecking balls on inner cities, older towns , and prized architectural artifacts.
Tourism also presents a hazard. It now generates $95 billion annually in international trade, a total second only to oil. Most countries are eager to show off their sights and sites so as to rake in tourists' dollars and yen. But tourism spurs modern development, and balancing such development with preservation of the old and fragile is a constant challenge. The charm and intimacy of old cities compete with the rampant construction of high-rise hotels. The sanctity and integrity of world-famous monuments compete with the need to provide adequate road systems and other tourist conveniences.
But a social consciousness pertaining to preservation has been widely aroused. Lessons have been learned and are now being generously shared. The exchange of information takes place daily through an international network of government and nongovernment organizations, as well as local groups in nearly every country. Preservation education is available at many colleges and universities.
''As a member of the World Heritage Convention,'' says Terry B. Morton, Chairman of US/ICOMOS, ''the United States is in league with 81 other nations working together under a formal program to identify, preserve, and protect monuments and sites deemed of exceptional value to the common heritage.''
Last week's conference here was titled ''The Challenge to Our Cultural Heritage: Why Preserve the Past?'' At it, S. Dillon Ripley, secretary of the Smithsonian Institution, summed up the preservationists' commitment:
''We have a deep conviction that the satisfactory future of the human race depends on the successful maintenance of both natural and cultural diversity, and we encourage global support for national programs in historical preservation.''