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

The deadliest diving spot in the world is also a stunning geological marvel.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Striking occult iconography on a medieval German church.

An ornate plague column – built to celebrate life – claimed the lives of numerous artisans during its construction.

This Slovakian statue of an emerging sewer worker might just be a bronze peeping tom.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

A spherical "micro-nation" in the heart of Vienna.

Baroque celebration of the end of the Great Plague of Vienna.

The maze-like transportation hub contains abandoned areas, derelict stores, and a resident bat colony.

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

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

World's largest crossword puzzle spans the side of a towerblock, its clues scattered throughout the city.

This Ukraine alleyway has become its own little island of forgotten things.

A fortress built to pacify local uprising that had a stint as a Nazi concentration camp before becoming a five-star hotel.

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

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

This ancient city - home to nine civilizations - is soon to be buried under 200 feet of water.

A sacred lake with thousands of sacred carp and a biblical history.

Descend 2,030 years into the past in an ancient tunnel built to support Jerusalem's most famous wall.

A musical instrument played by the sea.