Similar walls exist throughout the Inca Empire, including Cusco's famous 12-angled stone, demonstrating that these techniques were well-established Incan practices rather than alien intervention.

A sophisticated network of underground streets created by the Inca Empire has been discovered beneath the city of Cusco.

But the subjects were by no means as docile as the llamas, and many Andeans - dispossessed and exploited - bitterly resented the Inca as alien aggressors: "Inca tyranny is at our gate . . . If we ...