The Richat Structure in central Mauritania is a stunning geological structure 50 kilometers across (Wikipedia entry). Once thought to be an impact crater, it is actually a sedimentary formation that has eroded flat over many eons. Apparently there’s a hotel smack-bang in the middle of it.

There are also several other similar structures in the Sahara, such as the Jebel Uwaynat (thumbnail #2) which was used to define the borders of Sudan, Egypt and Libya, and also the Brandberg Intrusion in Namibia.

Even though none of these features are in high-resolution, it’s well worth zooming in a bit, as they’re perhaps even more fascinating to look at closer up.

Thanks to Pat Scaramuzza, Peter Nordstrom, GeMatt and Kai Huebner.