One of the few remaining ancient aqueducts described by Frontinus as 'the most solemn testimony of the Empire.'

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

A beautiful mountaintop mausoleum devoted to a Montenegrin icon can't seem to make everyone happy.

Hitler's bleak vision of relaxation still stands as a mostly abandoned 10,000-room resort complex.

An elevator into the Baltic Sea.

The ancient Greek Titan guards this massive dam holding a lightning bolt to symbolize electricity.

Religious structure known for its sculpted details.

Something's watching you.

Climbing to the top of the cathedral's bell tower offers sweeping views of these medieval ruins.

Once the legendary capital of the Dacian Kingdom, this city has been reduced to mere ruins.

This fairy-tale castle would make Dracula (who is said to have been imprisoned there) jealous.

An extraordinary museum devoted to the pop art legend created by Slovak artists.

The ruins of a 13th-century monastery that long served as a place of refuge from wars and raids.

Too much gossip or just missing curfew could land you in here for a couple of days.

An unusual cave filled with rare alien-looking aragonite formations.

A gorgeous stone viaduct crosses over a bucolic valley.

Inside the Šomoška National Nature Reserve exists a unique rock formation rarely seen in the world.

This ancient Roman bridge and aqueduct still stands as a wonder of classical construction.

The world's tallest boat lift stands as a massive piece of industrial tourism.

This wooden recreation of a 9th century lake village looks as though it was built yesterday (which it relatively was).

A colorful street named for the legendary Australian rock band.

Where commuters walk through remnants of an ancient Greek necropolis.

This small 16th-century church in Athens is almost entirely surrounded by a modern building.

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