Who made these circles in the Sahara?

An investigation that starts with a curious discovery on Google Earth and ends with a surprise in the middle of in the Sahara desert. This 30-minute video (it feels much shorter, trust me) is great on two levels: 1. The story it tells is fascinating. 2. It takes you behind the scenes of the investigation, showing you exactly how something like this is done. Feels like you’re right there, solving the riddle with them.