Go surfing on this urban wave, "hacked" by local surfers.

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

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

This elevator was built in 1907 to connect two neighborhoods separated by a steep, rocky cliff.

An underground network of massive stone arches and their skylit vaults support ruins of portico structures above.

Over the centuries, this island paradise has done it all, from providing monks with ecclesiastical respite to sheltering an exiled Leon Trotsky.

A marvel of Byzantine engineering under the streets of Istanbul.

A fountain standing as a testament to a doomed alliance.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Ancient serpentine sacrifice holder that has stood the test of time.

One of the most iconic neon ads of former East Germany.