A war-torn Olympic relic is being overtaken by graffiti and nature.

This former insane asylum now holds a pathological anatomy museum.

Natural cathedral designed by Italian artist Giuliano Mauri.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

The astonishing collection of an infamous criminologist.

The ancient abodes are a testament to human ingenuity amid harsh climates.

Mausoleum and Holy Seat of Antiochus I of Commagene.

Standing proud atop a Turkish bluff, this Ottoman palace has retained its grandeur despite being abandoned for centuries.

Underground monastery and fortress.

A shipwreck named Desire at the shore of Batumi.

A Turkish monastery tucked into a cliff wall.

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

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

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

An alien landscape on the banks of the Aegean Sea.

A Turkish ghost town abandoned in a population exchange with Greece.

This Irish show cave is said to have been the site of a Viking massacre that claimed 1,000 lives.

A rocky Irish outcropping with a history of wealth, conflict, and ruin.