OSLO -- Norwegian explorer Thor Heyerdahl says he faces the most exciting project of his life in a hunt for clues to a lost civilization that lies buried in a Peruvian city of pyramids.

Archeologists working in northwestern Peru last year found that 26 mounds, previously thought to be natural features of the landscape, were pyramids hidden by the ravages of time. The ancient city is called Tucume.

"This is the most exciting project I have ever been involved in," Heyerdahl, 73, told the Aftenposten daily in an interview recently. He will lead excavation work in Tucume next spring, in cooperation with Peruvian archeologists.

"The whole town is probably intact underneath ... It has never been plundered by grave robbers."

Heyerdahl has devoted much of his life to rewriting the history books on the peoples of the Southern Hemisphere, claiming that they were much more civilized than previously thought and that their culture was spread through sea travel.

In 1947, he crossed the Pacific in the balsa wood raft Kon Tiki to prove that ancient South American peoples could have traveled to the Pacific islands and populated them.

"A culture which is far older than that of the first Egyptian pharaoh must have been the basis for the spread of civilization," Heyerdahl said. "I hope Tucume will be able to put us on the trail of that lost culture."

Local Indian legends say that Tucume was founded by descendants of a king who brought his people to the Peruvian coast on balsa rafts. The pyramids are between 97 and 130 feet high.

Knut Haugland, director of the Kon Tiki museum that houses the famous raft in Oslo, said the museum would be working with Heyerdahl on the project.

"Archeologists started digging around one of the pyramids last year. They found gold masks, among other things, but we've only scratched the surface," he said.

"None of the other pyramids has been opened. We don't know exactly how old they are, but there must have been thousands of people living in that area. The finds made there will be of the greatest archeological significance."

Heyerdahl, who lives in Italy and is currently working in Egypt, said the Tucume project probably would take several decades to complete. He was invited to take part while on a visit to Peru last year.

Heyerdahl has pursued his career of ethnology -- the science of racial origins and characteristics -- with vigor for many decades.

His book on Kon Tiki has sold more than 20 million copies, and two years ago he visited Easter Island to try to find out more about its huge and mysterious stone statues.

In 1970, he succeeded in sailing a replica of an Egyptian vessel, called Ra II, from Morocco to Barbados in an attempt to prove that the ancient Egyptians could have reached the Western Hemisphere centuries before Christopher Columbus in 1492.