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

A traditional American farmhouse plopped in the middle of a Piccadilly courtyard.

London's smallest police station is barely the size of a phone booth.

A series of carved figures that scandalized British society.

Installed at a chaotic intersection, this gave London traffic cops a place to hang their heavy woolen coats.

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

This magnificently macabre shield shows the power of chivalrous love in medieval times.

A naturally mummified 2,000-year-old man.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

One of New York's best collections of pinball is hidden in a secret bar in the back of this laundromat.

2 square block factory in Greenpoint erected in 1936.

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

A forgotten relic from New York's bygone trolley system hides in plain sight under a bridge.

A 9-story, poured concrete structure which was used as a glue factory with an indelible smell.

Whether you're up or down, the Elevator Museum is worth a stop.

The best B-movies filmed on a shoestring budget were born here.

A fascinating insight into daily life in the Eastern Bloc.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

This classic restaurant features a gorgeous mirror-clad room.