Kuelap, the giant fortress built

The fortress of Kuelap or Cuélap (Chachapoyas, Amazonas, Perú), is a walled city associated with the Chachapoyas culture built in 6th century AD. It consists of more than four hundred buildings surrounded by massive exterior stone walls. The complex is situated on a ridge overlooking the Utcubamba Valley in northern Peru and roughly 600 meters long and 110 meters wide. It could have been built to defend against the Huari or others, but evidence of hostile groups at the site is minimal.

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