7. The Sacsayhuamán Walls
The imposing Sacsayhuamán walls above Cusco, Peru, are a masterpiece of Inca engineering.
Enormous stones—some weighing over 100 tons—fit together so perfectly that not even a blade of grass can slip between them, all without the use of mortar. How the Incas quarried, transported, and shaped these stones with such precision remains a mystery, leaving historians fascinated and perplexed. Learn more at National Geographic.
