World Heritage is big business, bringing hordes of tourists to poor countries that can use the jobs and the cash. It can also overwhelm the very sites it is designed to protect with all the less-savory aspects of mass travel, from chain hotels and restaurants to the impact of thousands of sport-shoed feet treading on fragile ground.

But World Heritage can also be an odd business, giving recognition to traditions (like premodern tribal dances and giant French family meals) that might have little aesthetic value to any group except the one that practices it.

Whatever the merits, the United Nations Educational, Scientific and Cultural Organization (Unesco) has embraced the concept. In fact, Unesco loves heritage so much that it has created two treaties to enshrine it.

The first, the World Heritage Convention, dating from 1972, builds on the notion of the United States national parks system, which was set up to defend a wild landscape before it disappeared. The second, the Convention for the Safeguarding of Intangible Cultural Heritage, was introduced in 2003 to defend traditions, not places, and is more controversial. Some 188 nations have ratified the first convention. To date, there are 725 cultural, 183 natural and 28 properties combining the two, in 153 countries.

The World Heritage list represents a catalog of marvels. Italy, needless to say, includes the Leaning Tower of Pisa (the whole Piazza del Duomo, to be fair) and Venice and its lagoon. Jordan has Petra and Wadi Rum. France even lists the banks of the Seine.

Russia has the Kremlin, Red Square and Lake Baikal. The United States lists Yellowstone, the Grand Canyon and the Everglades (cited as endangered). Independence Hall is on the list, but not the White House. Funny, that.

Luxembourg pretty much lists itself;Afghanistan includes the sad remains of the great Buddhas of Bamiyan, blown up by the Taliban.

In his book Disappearing World: The Earth's Most Extraordinary and Endangered Places, Alonzo C Addison, a director in Unesco's external relations department, arranges sites in varying degrees of distress from a variety of causes, including conflict, theft, development, pollution, invaders and tourism.

Conflict is the most obvious threat, whether in Afghanistan, Jerusalem, Kosovo or around the Preah Vihear temple on the border of Cambodia and Thailand, where there have been three armed clashes since the temple was listed.

The Darfur crisis has done extraordinary damage to the Garamba National Park in the Democratic Republic of the Congo and to the northern white rhinoceros there, killed for horns by militias seeking to buy arms, Mr Addison notes.

But most troubling may be the unintended consequences of mass tourism. Nations want to promote these sites for income. And good or bad, Mr Addison said in an interview, "The world is more global and some sites can't deal with all the tourists, " whether it's Machu Picchu or Angkor Wat. (Unesco is now trying to put Machu Picchu on the list of endangered sites. )

"The dark side, of course, is consumption, " said Francesco Bandarin, assistant directorgeneral of Unesco and head of its World Heritage Center, speaking of the consumerism that so often surrounds heritage sites. "And consumption and preservation do not go together. " If a site is "within an hour of a harbour, " he added, "it becomes inundated by a flood of tourism and geysers of money. "

Angkor, long isolated by war and the Khmer Rouge, he said, now has 200 hotels nearby. "This is a big problem now, " Mr Bandarin said. "The tourism industry has a lot of power in many poor countries but a short-term vision. "

UNESCO has drawn more criticism for its second convention, which focuses not on place, but on traditions. The Intangible Cultural Heritage list has been adding what are called "elements" only since 2008. So far, 139 countries have signed the convention, but not the United States. As Mr Addison said, "Even the word 'intangible' is hard for average people to get their heads around. "

There are 267 traditions enshrined so far, with 27 described as "in need of urgent safeguarding, " including "the watertight-bulkhead technology of Chinese junks. " The regular list includes oral traditions and performances, social rituals and crafts - from Cambodia's Royal Ballet to Indonesian puppet theater. And, perhaps peculiarly, the French gastronomic meal.

Cêcile Duvelle, the anthropologist in charge of Unesco's section for Intangible Cultural Heritage, fiercely defends it to those who think the idea too vague and subjective. "The word 'intangible' is recent, but the concept is old: the idea of nonmaterial culture and traditions, " she said.

The point, she emphasised, is not to "preserve and protect, which is to freeze something, but to safeguard. " Traditions can change as they are passed down, she noted, as a kind of living heritage that is continually recreated and evolving, yet provides a sense of identity. In return for listing them, governments commit to specific actions to promote, support and encourage them, whether it is a matter of altering or creating curriculums or even stopping deforestation.

Their inclusion implies that they may be in danger from modernisation and globalisation. While the US has hesitated to sign the Intangible convention, citing concerns about its implications for intellectual property rights, Washington's ambassador to Unesco, David T Killion, says that "World Heritage is critically important. " Countries fight hard "for the cultural branding rights, " he said. He points out that Herbie Hancock, a Unesco goodwill ambassador, would like to see jazz recognised as an Intangible Heritage.
And Paducah, Ky, is pushing for quilting.

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There are 28 Indian sites on the Unesco World Heritage list. The usual suspects include the Agra Fort, the Taj Mahal, Khajuraho Temples, Sun Temple at Konark and Qutub Minar but the Nanda Devi and Valley of Flowers National Park is also included. The last addition was Jaipur's Jantar Mantar in 2010.