Rome's semi-secret peephole vista is also a former Crusader stronghold.

The final resting place of this rock icon has become a pilgrimage site for AC/DC fans.

An abandoned NSA listening post on Berlin's "Devil's Mountain."

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

A church of bones, decorated with 40,000 human skeletons.

You've probably seen these distinctive orange-tiled columns on the big screen.

A mysterious shape catches the eye in this 16th-century painting.

This abandoned five-star hotel is now a five-star urban exploration destination.

This Western Australian mint was established during the height of the Australian gold rush.

Visible from both land and sea.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

A huge musical instrument played by the ocean.

The blinking light atop the iconic landmark has been sending secret messages for decades.

One of the best-preserved Roman amphitheaters is still used today, but for less brutal events.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

A micronation of epic proportions.

Living fossils in this remote Australian bay provide a glimpse of what Earth may have looked like 3.5 billion years ago.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

This bird-loving brewery is situated in an old municipal bathhouse, nestled beside a 300-year-old windmill.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

Alien rock formations grown from the sands of an Australian national park.

An abandoned marine theme park has created a difficult experiment in dolphin rewilding.

The ruins of a once prosperous power station have become a mouldering seaside gem.