Coober Pedy is a legendary opal mining town. (Apparently the name is an English corruption of the local Aboriginal term “kupa-piti” meaning “boys’ waterhole”.) Not quite Hobbiton, but the residents famously live in dugouts underground.
I stayed the night in the Lookout Mountain Underground Motel.
I immediately thought of the Vaults in Fallout 3 and the Silos in Hugh Howley’s Wool.
The walls show the gouge marks of the excavation equipment…
…a motif seemingly echoed on the toilet paper!
Although extremely well-insulated, a ventilation shaft pokes through to the surface which results in a haunting howl of distant wind. 
On the hill overhead, the ventilation shafts poke out aboveground.