The Sacsayhuamán citadel is located in which country?

To do all of that hard work at an altitude of over 12K is impressive. It's amazing to me that mankind has at times, been able adapt to some intensely stressful environments and circumstances.

Tony, by “12k”, Happy meant 12,000 feet elevation.

happydoghappycat, 3,701 metres is not 12k. But yes, still impressive.