15. Secrets of Lost Empires: Inca (2)

Even without such technological advances as wheels, arches, draft animals, iron tools, or a system of writing, the Inca—utilizing a tradition of shared labor—achieved a number of engineering feats. The NOVA team explores both stonework and bridge building, experimenting with dragging and fitting huge stones, and working with the people of an Andean village to create a suspension bridge made only of grass ropes.