Infamous marsh filled with toxic waste, World War II-era London rubble, and dead mobsters galore.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

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

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

A cement mixer-turned-kaleidoscope in downtown Norfolk offers different views of the city.

Where the sleeping monsters of Scotland's oil industry are left to rust.

Local legend says Isaac Newton built this footbridge without any screws, bolts, or nails.

Numberless clock creates a meal of time for the dreaded, insectile Chronophage.

A former fisherman's hut deemed too small for habitation is now a delightful tourist draw.

This ancient castle has been abandoned since the Edwardian conquest of Wales.

A real-life Professor Snape once taught in this Welsh university building, which students of course nicknamed “Hogwarts.”

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

A Roman spa buried deep beneath the City of London.

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.

After nearly 60 years, there's still a bear at Paddington Station looking for help.

This large, circular tomb is the final resting place of the first emperor of Rome.

Legend has it that this bronze orb, which sat atop an ancient Egyptian obelisk, once held the ashes of Julius Caesar.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

This ancient market is often referred to as the oldest shopping mall in the world.

This statue inspired by Renoir's famous painting embodies the jovial spirit of Key West.

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

An easy-to-miss garden in Boston's North End honors the mother of JFK and others who lost children in WWII.