This is the second time In the past couple of weeks that I've watched something regarding agricultural practices and the possible implications, that has amazed me.

On the documentary Hot Rocks, which is also fascinating, Scottish geologist Ian Stewart had a segment on Incan structures, that looked like large terraced stone amphitheatres. However, they weren't designed for watching games, but for growing crtops. Using this heat sink method, the Incas could successfully grow root vegetables and other crops at elevations of up to 12,000 feet.