A undated August 2004 photo shows archaeologists work on a stone citadel in a zone called Gran Saposoa, northeastern Peruvian jungle. US and Peruvian archaeologists have discovered five stone citadels pre-dating the Incan empire. The explorers, led by US archaeologist Sean Savoy, searched a 90-square-kilometer (35-square-mile) area and founded walls, squares and mausoleums in the Amazon region of San Martin, in a nearly inaccessible jungle area at an altitude of 2,800 meters (9,200 feet) above the sea level. AFP PHOTO/ANDEAN EXPLORERS FOUNDATION PERU-ARCHAEOLOGY