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

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

Winding paths and ramshackle mausoleums in the oldest "park cemetery" in London.

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

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

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

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

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

A Portuguese Jewish cemetery filled with stunning grave monuments that date back to 1614.

An overgrown and largely forgotten cemetery lies hidden within the outskirts of Amsterdam.

Seven mini rowhouses fill the gap between 54 and 70 Westerstraat.

This impressive collection of rare books on ancient mysticism inspired author Dan Brown.

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

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.

A once grand hotel now sits eerily abandoned in the Catalan countryside outside Barcelona.

One of Europe's largest supercomputers is housed inside of a disused chapel.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

This semi-secret storybook hedge maze is also the oldest garden in the city.

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