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

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

This legendary city has been a tourist attraction for centuries.

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

This ancient theater, restored in the 20th century, lives on as a venue for dramatic and musical performances.

This fortress dates back to the 6th century and is also the site of a controversial abandoned restoration project.

A spooky spot along the road where things mysteriously seem to move uphill by themselves.

A small town Romanian cemetery filled with darkly humorous gravestones.

A peculiar clock commemorates a historic victory won by ringing the noonday bell an hour early.

The world's greatest slide descends 18 stories from this looping mountaintop viewing platform.

This unusually shaped mountaintop tower looks like a UFO floating over the city.

This former quarry is now a picturesque gorge that hides a sunken lake.

An Orwellian sculpture with eyeball cameras watches passersby.

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

An old asylum graveyard that's been abandoned for half a century attracts those seeking a dark thrill.

The 14th-century ruins are said to contain healing powers.

This spherical sculpture has also been dubbed "the steel orange" due to its likeness to a massive, sliced piece of citrus.

This abstract sculpture once had a twin in Prague.

The soulless eyes of 82 bronze children stare on forever in remembrance of a horrifying World War II massacre.

This chimerical bridge/tunnel appears to dead end right into the sea.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

Sweden's "good old days" painstakingly re-created in a model village.

Stockholm's deepest subway station is also a stunning ecological wonder.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.