His body is said to have been exhumed, mummified and later hidden by his followers in the region in which the new site has been found.
According to legend, great treasures - which had been amassed for the ransom - were either buried with him, or separately.
Others believe the newly discovered site dates back far earlier, to unknown, pre-Inca cultures from before 500BC, citing what appear to be rudimentary tools found there.
The site is being investigated by a team of British, French, American and Ecuadorean explorers.
Among them is Bruce Fenton, an Ecuador-based Briton and researcher into the region's indigenous cultures, who has been involved in the project for about three months.
Also involved is Benoit Duverneuil, a French-American archaeologist, who undertook an expedition there earlier this year.
The vast wallslopes at a 60-degree angle, with a flat area at the top where many artefacts have been found. The team believes the summit was used for some human activities, possibly sacrifices.