There are lots of explanations for the gigantic structures built in China's desert. But the most mysterious thing is invisible: according to a former CIA analyst, there's someone who has ordered tons of satellite photos of this area since 2004.
And the plot thickens.
Allen Thomson, an analyst who used to work for the agency in the field of reconnaissance satellites, has noticed that "starting in 2004, somebody has ordered many, many satellite pictures of it".
You can see the extreme density of these requests if you turn on the DigitalGlobe layer in Google Earth — the satellite has received commands to photograph this area many hundreds of times. Compare that crazy grid of squares to the few images taken of its surroundings.
I doubt these orders come from the US military, since they have their own spy satellites — more accurate than Google's. Perhaps it's some low level agency not connected to the military. Or another country. Or Magneto. Whoever it is, Thomson points out to Wired's Danger Room that it "can't have been cheap".
Check out our original coverage of the structures here, along with more structures spotted by readers.