Yep, one interesting idea about these Amazon sites is that they add corroborating evidence to Francisco de Orellana (the first Spanish explorer to travel the length of the Amazon) that he claimed he had found huge cites with hundreds of thousands (maybe millions) of people living in the Amazon basin.

Presumably by the time later explorers came along 50 years later to verify his claims, the people had all been killed by European diseases like small pox and the jungle had claimed back the cities.

https://en.wikipedia.org/wiki/Francisco_de_Orellana