The underground houses of Coober Pedy (Pic heavy)

Coober Pedy is a town located in northern South Australia and is known as the opal capital of the world, as nearly 95 percent of the world's opal supply comes from the local mines. This small town with a population of around 3000 has a unique way of life – nearly half of them live underground.

Back in 1916 when people moved into Coober Pedy to mine opal, the harsh summer temperature drove them into caves dug into the hillsides. When temperatures outside raged over 40 degree centigrade, underground temperatures remained comfortable and nearly constant year-round. Even today, the town folk prefer to build their homes in underground caves. In fact, many of these homes are abandoned mine shafts dug to search opal.

Coober Pedy has around 250,000 mine shafts ...

http://35mm.instantfundas.com/2008/11/underground-houses-of-coober-pedy.html

Wonder how fresh air gets into the caves.

as well. Natural air conditioning.

Caves blow out when it is warmer on the surface and pull in when it is cooler.

wow comes to mind when I look at them pictures. I've bookmarked this site so I can send links to all I know.
Thank DPP, I hope you have a great day.

a rich dude waiting for "end times" had a natural cave converted into a house. But the drips from the moisture has been a problem. It's now a B&B (rich dude sold it).