Pagan monument converted to Christianity with the population.

Hamburgers are intensely proud of their tunnel beneath the river.

Once the tallest building in the world, this abandoned church is now a monument to the destruction of WWII.

Op-art architecture designed for happiness.

The house that took a plunge into the facade of a museum.

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

Beautiful Austrian natural history museum with carved ceilings and row after row of ancient taxidermy.

A miniature train-ride through Slovenia's largest cave system.

Debatably clever, or just plain honest hotel advertised as "The Worst Hotel in the World."

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

A beautifully eclectic mix of architectural styles.

Steadily reminding Czechia of its past.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.

This automated sculpture of two men peeing will spell out text messages with their micturition.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

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

Blitzkrieg bop your way through Berlin's Ramones Museum.

Thousands of coffin-like pillars make up this controversial Holocaust memorial.

The most visited, and possibly most controversial, museum in Germany.

Possibly the world's largest hourglass only needs to be reset every New Year's Eve.

Tucked away near more famous landmarks lies a statue meant to symbolize the confluence and continuing development of human culture.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

Abstract monuments express sorrow and resilience at the site of a horrific massacre in Nazi-occupied Serbia.