LIMA, PERU (AP).- Tourists love the enigmatic Inca citadel of Machu Picchu high in Peru's Andes. They may love it too much.

As the country prepares to celebrate the 100th anniversary of the rediscovery of the "Lost City of the Incas" on Thursday, archaeologists are warning that a heavy flow of visitors and poor administration are threatening one of the wonders of the world.

The Incas built Machu Picchu atop an Andean peak 7,970 feet (2,430 meters) high, with a breathtaking view across the inhospitable abysses that surround it. Some experts believe it was a refuge for one or more Inca rulers, others that it was a religious sanctuary.

The site receives an average of 1,800 visitors a day and the maximum allowed by authorities is 2,500. Already, the former farming village of Aguas Calientes that is used as a jumping-off point for tourists has grown into a town of 4,000 inhabitants with five-star hotels and restaurants.

In some places, authorities have noticed soil erosion and damage to vegetation, Juan Julio Garcia, regional director of Peru's culture ministry, told The Associated Press.

Tourism companies and some local officials constantly pressure authorities to allow even more tourists, arguing it would benefit local communities.

Cultural guardians fear irreparable damages if the tourist flow surges, and they are especially concerned by official plans to build a highway to the remote 15th-century ruin.

Tourists now must reach Machu Picchu by foot or by a scenic, zigzagging narrow-gauge train ride.

"In one way or another, the train controls the flow (of tourists). There is a maximum capacity on the train and this maximum capacity determines how many people can reach the monument. In contrast, with a road, any person or tourism company can reach the site and try to enter the sanctuary," Garcia said.

But rains washed out the rail route in January 2010, trapping 4,000 tourists in the towns of Machu Picchu and Aguas Calientes for five days. Without road access to the area, the government had to airlift tourists out by helicopter. In Aguas Calientes, which serves as a tourist base for Machu Picchu, there were shortages of food.

In September, Peru's Congress approved construction of an access road to Machu Picchu.

That raised a red flag at UNESCO, which inscribed the Inca stronghold on its World Heritage list in 1983, boosting the site's fame and making it eligible for international technical support. The U.N. agency had already expressed concern about management of the site. It said in 2008 that there were "urgent problems with deforestation, the risk of landslides, uncontrolled urban development and illegal access to the sanctuary."

The U.N. agency threatened to put it on its list of endangered sites if the road project is not canceled, a move that would be a blow to Peru's prestige.

Peruvian tourism authorities insist they are protecting the monument. Carlos Zuniga, head of the Foreign Trade and Tourism office for the Cuzco region, said that officials have given UNESCO proof of concern for Machu Picchu by completing a plan for use of the sanctuary and by issuing a decree that funds generated by tourism to Machu Picchu be used in maintaining the site. Previously, earnings were sent to the central government in the capital, Lima.

Garcia, of the culture ministry, said local authorities support the highway project because they want to break the monopoly of PeruRail, the train company owned by Chilean and British interests. Aguas Calientes Gov. Antonio Sinchi Roca said the monopoly hurts the local economy. "Many entrepreneurs who could reach the zone don't because the cost of transportation is so high."

Machu Picchu was largely unknown to the outside world, abandoned and covered in highland jungle, until July 7, 1911, when Yale University historian and explorer Hiram Bingham reached Machu Picchu and later announced its existence. He became famous as the site's modern discoverer, though Peruvian Agustin Lizarraga had been there first. He wrote on one of the citadel's stones with a piece of charcoal: "Lizarraga, July 14, 1902, for posterity."

For decades, the site's remoteness, as well as the cost of reaching it, kept foreign tourists at bay. In the 1980s, visitors shunned Peru because of a raging guerrilla conflict that ended in 1999.

In 1991, about 77,000 tourists visited. That number has risen about tenfold over the past decade, reaching more than 800,000 in 2009, the year before the rail line washed away.

The director of Machu Picchu Archaeological Park, Fernando Astete, said the main problem facing the site today is that the area is controlled by rival municipal authorities contending for tourism dollars.

"Local authorities in and around the zone don't know what UNESCO is, they know nothing about it. They don't know they are in a protected area," Astete told The AP.

Many authorities view the citadel as "a marketing issue" and don't make decisions based on technical criteria about conservation of the site, Garcia said.

An example occurred in 2000, when a beer company was allowed to film a television commercial in Machu Picchu. The heavy arm of a crane used in the filming fell onto and damaged the emblematic Intihuatana Stone, which many believe to be sacred.

This didn't stop authorities from recently permitting the filming of dance scenes for the Bollywood movie "Endhiran" ("The Robot"), starring former Miss World Aishwarya Rai.

Peru's government had planned a big celebration in the ruins themselves for Thursday's anniversary, but called that off when UNESCO objected.


Copyright 2011 The Associated Press.