This NASA photo taken from the International Space Station shows crop circles in southwest Egypt's Sahara Desert. The crops thrive in the middle of the desert thanks to either secret alien technology or the amazing underground Nubian Sandstone Aquifer System that covers two million square kilometers. From the NASA Earth Observatory:
The crop circles are a result of center-pivot irrigation, an efficient method for water conservation in agriculture. Groundwater from the Nubian aquifer is drawn up from wells in the center of the circles, and it is sprayed or dripped out of long, rotating pipes that pivot around the center.
Most of the crops pictured here are likely potatoes (darker green circles), wheat (lighter brown circles), or medicinal and aromatic plants such as chamomile. The light, tan-colored crop circles likely have undergone controlled burning to remove excess plant matter and essentially clean up the land for the next crop.