While not Turkey's deepest underground city, this subterranean redoubt is the largest.

This ancient subterranean megalopolis is known for the hot oil traps that were installed above each of its entrances.

Sitting on an Italian hilltop is this surreal fortress built by the mad inventor of electrohomeopathy.

Rather than a run-of-the-mill franchise hotel, this lodging has been decked out in dinosaur decor.

This Navarrese cave's history of witchcraft and pagan ritual is not just embraced, but recreated each year.

The winter home of millions of migrating monarch butterflies.

This naturally-sourced hot spring is now home to a clothing-optional resort.

A multi-storied adobe complex has been inhabited for more than a thousand years.

The scene of one of the darkest moments in American labor history has been left essentially untouched since the tragedy.

Silver in the hills led to the speedy creation of this boom town and a lack of it saw the town abandoned nearly as quickly.

Abandoned Nazi train station turned underground astroparticle laboratory.