This set of Inca ruins is close to Cusco, the ancient Inca capital. The stones are so giant and so smooth and so well joined together that nothing our guide could tell us would help it to make sense. Somehow people had quarried and shaped and fit these boulders together five hundred years ago, without the use of the wheel or even hard metals, like iron or steel. They may have used rope or streams of water, they say, to carve the blocks into such perfect building stones.