One autumn day in 1982, Thor Heyerdahl received a letter in the post. The envelope contained a photograph of a hitherto unknown stone statue from the island kingdom of the Maldives in the Indian Ocean. It enticed him to launch an archaeological expedition, to find out more about those who had made the statue in the photograph.

In the period 1988–1992, Thor Heyerdahl led archaeological excavations of the pyramid complex "La Raya" in Peru. In the area there were 26 pyramid-like constructions of sun-dried clay, so-called adobe blocks. The archaeologists concluded that the ruined city outside Túcume was built around 1100 AD.