Dating back almost 400 years, the oldest public collection library in the United Kingdom was once the study hall of Karl Marx.

A Roman spa buried deep beneath the City of London.

The 2,000-year-old beam is tucked within the pedestrian entrance to the old London Bridge.

Eclectic final resting place of the controversial explorer.

At 929 pounds and 26 feet tall, this stainless steel fork can only be used by the likes of King Kong.

The bizarre visions of H.R. Giger, tucked away in a Swiss medieval city.

This medieval church tower has maintained its clockworks since the 16th century.

This beautiful deer park was built so King Charles I and his court could go hunting while escaping a deadly plague outbreak.

The sumptuous ceiling was one of the last things Charles I saw before his execution.

The Tudor-style cottage in the middle of the square is not quite what it seems.

A sculpture outside London's oldest cathedral honors the Mohegan chief who died while petitioning the king.

A monument to the thrice mayor of London who according to lore made his fortune by selling his rat-chasing cat.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

A statue marks the exact spot where The Boy Who Never Grows Up made his first literary appearance.

A hidden treasure in London with a rich medieval history, and the resting place of many luminaries.

Rebuilt remains of a temple to Roman god Mithras.

A hands-off space for graffiti artists to hone and display their skills.

This whimsical statue dumps water on its head to symbolize knowledge flowing into his brain. Or maybe booze.

A rare example of World War I trenches from the British front.

A floating cat sanctuary on an Amsterdam canal.

An ancient octagonal weather station named for the eight Greek gods of wind.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

Stockholm's tiniest statue is of a small boy looking at the Moon.

This early Norman castle was the first historical monument protected by an act of Parliament.