4. Coober Pedy, Australia

The interior view of a Serbian underground church in Coober Pedy, South Australia. [Photo/IC]

Around 3,500 residents of the mining town of Coober Pedy in southern Australia live underground, in dugouts or mud caves.The town even has churches, museums, art galleries, a bar and hotels for travelers to experience the underground life first-hand.

Due to the heat, it is one of the world's most inhospitable regions, which explains its residents being happy to dwell in subterranean homes.