Inca fortress of Sacsayhuamán near Cusco, Peru

The (Inca) empire strikes back

Back in the 1530s, Spanish conquistadors were tightening their grip on the lands of the Incan Empire, including the massive 12th-century stone fortress in today's image: Sacsayhuamán, in the old Inca capital of Cusco. The Spanish held a man named Manco Inca prisoner, the puppet leader they installed over the Incans. But one day in the spring of 1536, he escaped.

He returned on 6 May, accompanied by legions of Inca warriors. The Inca retook much of Cusco, including Sacsayhuamán, which they made into their main base, forcing the Spanish to take refuge in buildings near the main plaza. In the end, the Incan effort failed: After a few months, the Spanish retook Sacsayhuamán and cut off the Incans' supplies, forcing their surrender and finalising Spain's control over Peru. The Spaniards partly dismantled Sacsayhuamán and used its smaller blocks to build colonial Cusco. But even today, the outer walls of impossibly large interlocking stones still overlook the modern-day city, a symbol of the mysterious empire that once ruled here.