Visitors to Machu Picchu see well-preserved ruins hidden among the majestic Andes: palaces, baths, temples, tombs, sundials and farming terraces, along with llamas that roam among hundreds of gray granite houses. However, curious tourists won't find many bowls, tools, ritual objects or other artifacts used by the Incas of the late 1400s.

To see those, they have to go to New Haven, Conn.
Yale historian Hiram Bingham rediscovered Machu Picchu in 1911, and backed by the National Geographic Society, he returned with large expeditions in 1912 and 1915. Each time, he carted out crates filled with archaeological finds, with permission from Peruvian President Augusto Leguía.

Today, Peru is threatening to sue the Ivy League school, claiming the permission was either given illegally or misunderstood.

The treasures of Machu Picchu, says David Ugarte, regional director of Peru's National Culture Institute, were given to the American explorer "on loan."

Peru's battle with Yale is not unique. Since 1820, when Greece demanded the return of the Elgin Marbles from the British Museum, countries of origin have steadily gotten more assertive about retrieving their heritage.

In a case last month, Italy demanded that the New York Metropolitan Museum of Art hand over the Euphronios Krater, a vase dating to 500 B.C., along with other objects.

"This is our patrimony. This is everything to us — proof that even though today we are poor, our ancestors lived great and proud," Ugarte says. "Bingham said he was going to study those pieces and give them back. It was clear to all they were to be returned."

Yale disputes Peru's claim but has offered to return part of its Machu Picchu collection.

The university, in a letter Dec. 8 to the Peruvian government, said, "The civil code of 1852 ... in effect at the time of the Bingham expeditions, gave Yale title to the artifacts at the time of their excavation and ever since."

Colin Renfrew, professor of archaeology at Cambridge University in England, says the case hinges on one question: "What was the deal between Bingham and Peru at the time?" The answer, he says, "is very murky."

Ugarte says Peru began sending Yale requests for return of the pieces — or for negotiations on the issue — starting in 1917.

The university "always wrote back with different excuses," he says. "First, they said they needed more time to evaluate the pieces, then in later years said they were studying our requests for the return."

With the 100th anniversary of the city's rediscovery five years off, Ugarte says, Peru has had enough.

President Alejandro Toledo and his wife, an anthropologist, have made retrieval of the objects a priority before Toledo, Peru's first indigenous president, leaves office in July.

The Peruvian government has notified Richard Levin, Yale's president, that it will sue if the archaeological pieces aren't returned. Guillermo Lumbreras, director of the National Culture Institute, says the case would first go to Connecticut state courts but might ultimately wind up before an international tribunal.