Machu Picchu
How did the Inca raise a stone city on a knife-edge Andean ridge at 2,430 meters — terracing near-vertical slopes, fitting granite blocks so tightly a blade won't slip between them, and hiding a drainage system beneath it all — so well that it has outlasted five centuries of torrential rain and earthquakes?
early-to-mid 15th century CE (Inca, reign of Pachacuti) · Machu Picchu, Cusco Region, PeruAdded July 2026