Hiding the longest subterranean river known in the world.

A monument to the thousands of Canadian soldiers who died capturing the French ridge during World War I.

The 16th-century church was kept in its ruined state as a reminder of the casualties of World War I.

These crumbling Nazi artillery bunkers are now fair game for massive graffiti projects.

An astounding collection of taxidermy, fossils, skeletons, and even a few strange live beasts.

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

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

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

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

The last four extravagant street signs of London's historic banking street.

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

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

Eighty million natural history specimens call this gargantuan museum home.

This triumphal arch celebrating the Sun King's conquest of Lille is a masterpiece of military architecture.

A measuring mishap led to these artificial stone ladies losing their stomachs.

The curios of pharmacist and collector Henry Wellcome.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

The second-largest gold nugget in existence, displayed in a Las Vegas casino conveniently named the Golden Nugget.

A giant donut stands as a popular symbol of Los Angeles iconography.

Crypt mausoleum in cathedral's basement contains relics of third century Roman martyr, Saint Vibiana.

The "Fun Spot of the Desert" is now a haunting ruin, and a reminder that putting a water park in a desert is a bad idea.