Sacsayhuamán

Hundred-ton stones fitted like wax. Not even a knife blade slips between them.

Sacsayhuamán's zigzag walls fit irregular polygonal stones up to ~120 tons with mortarless precision. Spanish chroniclers already marveled; Inca accounts attribute it to earlier builders. Archaeology demonstrates Inca techniques (pounding stones, trial fitting) at smaller scales; the largest blocks' logistics remain debated. Part of the megalithic cluster with Baalbek and Puma Punku.