There’s an opal mining town in central Australia named Coober Pedy. As the temperatures on the surface tend to hover around the 50°C mark, most people live underground.
The opal is scattered over a field a few hundred kilometres wide, and the town is built bang in the middle of it; there’s opal underfoot. But in order to minimise noise and dust, there’s a rule forbidding mining within the town limits.
However, if you just happen to stumble across some opal while you’re digging a new room for your underground house, you’re allowed to keep it.
As a consequence, Coober Pedy is now full of single men who live in gigantic underground mansions with a dozen bedrooms each.
