People escaping slavery may have hidden inside a corpse vault.

A derelict bit of transportation infrastructure hidden in the woods.

A relic of FDR's brief foray into utopian urban planning.

A fortified medieval basilica on the Caelian Hill preserves extraordinary frescoes and one of Rome's most beautiful hidden cloisters.

A Nesting Doll of Churches.

An archival collection of over 2,200 case studies which includes human brain specimens and tumor specimens.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

The shelves in the back of this thrift store are devoted to saving, not selling, retro tech.

An intricately designed junk art house with four extravagant junk art cars hidden in the suburbs.

This abandoned asylum was once a state of the art facility before devolving into one of the most deadly mental institutions in American history.

A Spiritualist house of worship where believers communicate with the dead in the spirit world.

This grand gothic brewery has been pumping out suds for over a hundred years.