One of Amsterdam's narrowest houses is located right across the canal from its widest.

Widely advertised as Amsterdam’s narrowest street, this passage was once a highlight of the Red Light District before its windows closed.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

Tucked in the back of a flower shop, its collection details the fascinating history of the Netherlands's iconic symbol.

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

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

An abandoned concrete jungle surrounded by a lush park.

Community bookshelf of 25-foot-tall book spines.

These thermal springs were once popular with residents of a nearby Roman colony.

For over 300 years this little carving has been the city’s good luck charm.

Peeing dogs guard the Roman hunting goddess atop a fountain at France’s Château de Fontainebleau.

A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

Trek into the depths of the cave where 17,000-year-old paintings exist alongside 400-year-old graffiti.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

Graffiti from the 16th and 17th centuries cover the walls of this part of the Tower of London.

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

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

What might be the oldest living tree in London has survived fires, bombings, and estate agents.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

This ancient Egyptian obelisk still bears the wounds of World War I.

A haunting monument dedicated to the Royal Naval Air Service and the Fleet Air Arm.

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.