The World Monuments Fund on Tuesday released its biannual watch list of global architectural treasures at risk from urban development, tourism, neglect and bad planning.

The 2010 list comprises 93 sites in 47 countries, including ancient structures but also 15 that were built in the 20th century and are already deemed endangered classics.

Some sites, like the traditional wooden houses of Kyoto in Japan, or thatched royal tombs in Uganda, may be modest from an architectural standpoint, but represent immense cultural and historical riches.

The list also includes Peru's breathtaking Machu Picchu ruins, the Gaudi-designed Sagrada Familia church in Barcelona, and iconic US architect Frank Lloyd Wright's Taliesin and Taliesin West houses.

The common factor was "places that define and enrich our lives and our environment ? and our world wouldn't be the same without them," Bonnie Burnham, the fund's president, said.

"They're on the watch list because they're losing ground," she said.

One of the biggest culprits, according to the World Monuments Fund, is intense urban development, with high-rises and other modern buildings blamed for killing the character of ancient cities like Kyoto.

In Seville, southern Spain, the romantic old center is carefully protected, but a plan to build a skyscraper just outside that zone threatens the landscape, Burnham said.

Tourism brings other challenges, the fund said, highlighting the mysterious, circular ruins of Chankillo in Peru.

Tourism is 'not the villain'

Burnham called Chankillo potentially "the next Machu Picchu in terms of adventure tourism," but stressed that poor management, not the number of visitors, was often the real problem.

"The tourism industry is not a villain here. Generally it's a lack of real will power by the locals and owners of the site," she said. "These are really planning issues."

Some causes on the list are already close to being lost.

For example, a trove of 50 000 petroglyphs on boulders in Pakistan is about to be submerged in water from the Diamer-Bhasha dam.

But in many cases relatively modest funding can make a big difference by helping with planning, the fund said.

One treasure targeted for protection is the Native American complex at Taos Pueblo in New Mexico, a place of continuous inhabitation for some 1000 years and now under growing tourist pressure.

The challenge, a Native American representative said, is not just to maintain the adobe buildings, but to ensure respect for the site's less visible attributes.

"This is a living monument. It's a living site. It's a sacred site. It's sacred to us because that's who we are," said Luis Zamora, sporting beaded moccasins and a colorful blanket over his shoulders.

"If you've ever been there, then you will feel the spirits," he said.