A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

This Italian foot path winds through the mountains via 52 individual tunnels.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

Nestled on the banks of a river in Nuremberg is a small museum that was once home of the city's official executioner.

This abandoned coliseum was intended to be a grand Nazi rallying ground before it was halted at the end of the war.

When the rain falls, this drain system turns into a musical instrument.

The birthplace of an eccentric alchemist and possible inspiration for the fictional reanimator of monsters.

Sweden's "good old days" painstakingly re-created in a model village.

A temple to modernity, tucked away amid Barcelona's more well known museums.

The oldest giants in Catalonia are now displayed in a 14th-century Gothic church.

Gaze upon chocolate sculptures depicting everything from chariot races to Gaudí's famous church at this shrine to sweets.

A completely underwater art museum sends a stark message about humans' impact on the environment.

These striking ruins of a castle resemble a ship's stern.

Hundreds of caves once used to store grains and animal feed.

A stately palace has been converted into the world's largest cannabis museum.

18th century anatomical amphitheater of the Royal College of Surgery of Barcelona.

Mountain where Jesus was first tempted by the Devil.

Village situated on a narrow volcanic escarpment.

Week-long block party becomes a competition for the best decorated street.

A gravity-defying "devil's bridge" that has a surprising architectural feature for its stability.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

This cemetery features modernist statues as strange as its name.

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

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