Sky Caves of Mustang Kingdom, Nepal

The Sky Caves in Nepal are called so for a reason: they are carved in the cliff in a gigantic Himalayan gorge, 155 feet from the ground. These caves are either dug into the cliffside or tunnelled from above. The number of caves is bizarre:

there are 10,000 of these human-made caves, ensconced in the fragile, sand-coloured cliffs, and they look like a giant sand-castle, standing in the middle of a neighbourhood in the sky. Found in Central Nepal in the former Kingdom of Mustang, these caves are assumed to have been built thousands of years ago, but, who built them and for what purpose are still archaeological mysteries. Some of the caves have eroded murals on the walls.