Apartment complexes built into huge repurposed natural gas tanks.

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

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

The beautiful baroque library of the Hapsburg empire.

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

Legends surround an ancient tree trunk riddled with nails for good luck.

A former top secret nuclear fallout shelter now operates like a hotel stuck in the Cold War.

Europe's second largest ossuary wasn't discovered until 2001.

An abandoned dollhouse factory.

The walls of America's oldest masonry fort famously "swallowed" cannonballs.

An 18th-century Spanish watchtower made entirely of seashell and concrete.

One of the oldest, tallest, and most haunted lighthouses in America.

The last living thing to come out of the rubble after 9/11 is now a symbol of hope and resilience.

Cozy basement bar sports an inventory of over 2,000 beers.

Brussels' favorite peeing boy has a sister.

Christ's blood allegedly preserved in a Belgian town.

This triumphal arch celebrating the Sun King's conquest of Lille is a masterpiece of military architecture.

This narrow Ghent alleyway is an officially sanctioned street art tunnel.

Three floors of musical instruments coming from all corners of the world and hundreds of years of musical history.

Thirteen pastel palaces in downtown Charleston add a gorgeous splash of color to the city.

A unique work of art that was created without permission.

The attic of a four-century-old canal house hides a clandestine church.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.