Kuelap, in Peru, boasts an ancient mountain fortress surrounded by a massive stone wall. It's at the center of a once-thriving metropolis, abandoned half a millennium ago. The stone ruin remains a mystery - but now you can visit it.

According Atlas Obscura:

Kuelap, a mountaintop fortress city, rivals any ruins in the new world and comes complete with living quarters for thousands of residents and a stone wall fortification reaching 60 feet high running in circumference to the city.

Kuelap is considered the largest stone ruin site in the New World and is comprised of massive stone blocks nearly 10-times the volume of the blocks used in the Giza Pyramid.

The fortress of Kuélap consists of massive exterior stone walls containing more than four hundred buildings. The structure, situated on a ridge overlooking the Utcubamba Valley in northern Peru, is roughly 600 meters in length and 110 meters in width and is thought to have been built to defend against the Huari or other hostile peoples. Archaeological evidence shows that the structure was built around 500 AD and occupied until the mid 1500s (Early Colonial period).

Read more about this awesome ruin via Atlas Obscura

Images of Kuelep via Photobucket stream