High Victorian fantasy created a fairytale castle out of a ruined fortress in Wales.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

A garden in Lisbon filled with giant porcelain creatures.

A madman's personal garden filled with 1,000 sculpted heads.

Street artists transformed an abandoned air vent into the beloved Star Wars robot.

It houses the remains of a 17th-century version of the Titanic.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

Six beautiful wooden giants are hidden around Copenhagen.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

Hans Christian Andersen for the postmodern world.

Hidden beneath the streets of London is a secret subway that only carried mail.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

Budapest's Communist-era statues, banished to the suburbs.

Uh, pardon me, ma'am, but I couldn't help noticing that there's a Columbo statue in the middle of Budapest.

Tucked away near more famous landmarks lies a statue meant to symbolize the confluence and continuing development of human culture.

The tunnel's elegant proportions keep you snug with no claustrophobia freak-out.

A mocking tribute to the past and modern leadership of Prague.

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

This elaborate Byzantine-style building was designed for a not-so-pretty purpose.

Banksy gives themself artistic license with this piece of London street art.

The cedar tree in Highgate Cemetery earned its title by accident.

You'd never know the houses at 23-24 Leinster Gardens were fakes—until you see the train tracks on the other side.

Shakespeare, David Bowie, Dr. Who, the Saxons, Druids and Romans are all claimed to have all made their mark on these massive man made tunnels.

In Twickenham sits a small whitewashed castle that inspired Mary Shelley's 'Frankenstein.'