A line number in Amsterdam that will likely never be used again due to its tragic history.

This subterranean studio is filled with fascinating kinetic art.

From Nazi chemicals to the CIA, this architectural marvel has played a fascinating role in German history.

Seven mini rowhouses fill the gap between 54 and 70 Westerstraat.

The last of Amsterdam's original sea level markers remaining in place.

The tallest waterfall in the Netherlands is a lovely, stepped feature that is only 50 feet tall.

Tucked away in the Leiden city hall are a group of works by famed artist MC Escher.

Unchanged for centuries, this medieval library keeps its books in chains.

A seven-century-old jail tells a not-so-pleasant history of crime and punishment.

Go inside a revolutionary, cage-less zoo where 70 species of monkeys roam free alongside their human visitors.

This surreal statue brings a famous French novel about a supernatural cad to arresting life.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A unrivaled and rather horrifying collection of wax dermatological models.

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.

Hidden away in a modern library are the remains of one of the 18th century's most celebrated wunderkammers.

Indents in the pavement are all that remain from a grisly death machine in Paris.

The mark of the Devil's horns on a marble column in Milan.

Before there were doorbells this bronze ear was installed for visitors to announce their arrival.

A former plague hospital turned medical museum.

Thousands of costumed dolls fill one of the world's creepiest museums.

For a brief time in 1960s France, families could climb into a tiny submarine and be pulled along an underwater journey.

The former home of a mad diplomat is said to still be marked in bloody, arcane scrawls.

Oldest Museum of the Netherlands is a true cabinet of curiosities.

A curious collection dedicated to human and animal anatomy and pathology.