A flamboyant five-story building in Bulgaria resembles a crawling snail.

This exclusive resort has completely covered a tiny Balkan island in a 5-star warren of guest rooms.

A curious cave church carved into the face of a cliff.

A sixth-century Byzantine cistern hidden below a modern carpet store.

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

A mysterious ancient cemetery with Roman sarcophagi and Lycian inscriptions.

A Turkish monastery tucked into a cliff wall.

Roman ruins, natural methane fires and a lovely beach.

This hunter-gatherer architecture is believed to be the oldest religious complex known.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

Packed to the ceiling with antique taxidermy and hunting arms.

This eccentric folly house was designed by Romanian thinker Bogdan-Petriceicu Hasdeu, with a helping hand from his deceased daughter's spirit.

Check out engineering marvels of the past at this unintentionally retrofuturist museum.

Hundreds of thousands of concrete bunkers crowd Albania long after the fall of Communism.