Inca

The engineering skills of the Inca were great, even by today's standards. An example is the use of pieces weighing in upwards of one ton in their stonework (e.g., Machu Picchu in Peru), placed together so that not even a blade can fit in-between the cracks. The villages used irrigation canals and drainage systems, making agriculture very efficient. While some claim that the Incas were the first inventors of hydroponics, their agricultural technology was still soil based, if advanced. This technology, including tiered farm plots, allowed significant yields from steeply sloped or otherwise unproductive land. They mined gold extensively, one of the objects of the Spanish conquistadors, and created a network of paths and roads connecting their many towns and villages. River gorges were crossed by roped suspension bridges, the rope made by braiding grasses.