SubTropolis

SubTropolis wasn't the first to make use of the underground environs of a disused mine. During WWII many precious cultural artefacts were stored in old mines, for example. It does seem to be the largest and most modernised though. I do wonder why we don't make use of what's below ground more often (especially in the UK where cellars/basements are very rare). Not sure I'd want to live there full-time though.

via io9