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

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

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

A monument to the three wars that led to German unification towers within a Berlin traffic circle.

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

An early 20th-century bullring converted into a modern shopping center.

Mountain where Jesus was first tempted by the Devil.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

This large copper bolt represents the benchmark for measuring sea levels in most of Europe.

Europe's official "zero-level," the equator of elevation.

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

Amsterdam's former hotspot for public executions and dissections.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

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

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.