This symbol of Polish heritage survived the occupation during World War II, hidden in plain sight.

An abandoned Nazi explosives plant founded by the inventor of dynamite is now an underground museum.

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

A mysterious structure left behind on the Polish mountainside, sometimes called "Hitler's Stonehenge".

The celebrated eyesore created by starry-eyed sweethearts.

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

Climb around the high waterfalls on series of iron ladders and bridges within the wildest gorge in the Slovak Paradise.

The 700-year-old fortress was the site of Count Orlok's castle in "Nosferatu."

It houses the remains of a 17th-century version of the Titanic.

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

This Belgian theme park began as a refuge for bored church children and was closed down when a boy lost an arm.

Eighty million natural history specimens call this gargantuan museum home.

These Egyptian statues have survived for 3,400 years and were an acoustic wonder of the ancient world.

Deep in a Polish forest, this collection of Iron Age megaliths still holds onto many of its ancient secrets.

A merchant court dedicated to the fictitious King Arthur is heavily adorned with bizarre Renaissance art.

A cluster of headless, armless sculptures looms within a popular Polish park.

This Transylvanian church has changed its denomination four times.

The European towns of Brașov and Râșnov each have proud signs reminiscent of the Hollywood sign.

This elaborately decorated, fairytale-like Romanian royal palace is one of the most striking castles in Europe.

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."

Something's watching you.

Even drowned in an ocean of toxic waste, the remnants of this Romanian village stand tall.

This massive underground salt mine now holds a sci-fi theme park in its depths.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.