Amazing and mysterious Neolithic settlement on Scotland's Orkney Islands.

One part local history, 99 parts gruesome haunted house.

The most iconic structure in Scotland has been home to bishops, colonels, and Sean Connery characters.

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

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

A 30-acre garden inspired by the principles of modern physics.

The hidden "ballroom" under a mansion lake was built by a criminal who ate a cyanide pill during his trial.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

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

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

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

This huge abandoned fortress hidden inside a mountain holds a world of subterranean secrets.

A medieval village holds a very modern hotel.

An archeological treasure trove stumbled upon by a couple of children.

Hundreds of stone stairs and a winding medieval bridge connect this haunting Spanish island to the mainland.

Sanctuary on a ridge near an ancient shrine to a "Black Madonna" built by the founder of Opus Dei.

An arresting arch punched straight through a mountain provides one of the most scenic spots, and challenging climbs, on the planet.

Abandoned Nazi train station turned underground astroparticle laboratory.

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

Abandoned 18th century weapons factory in the Aezkoa Valley.

A brush maker used his factory to protect blind Jews from the Gestapo.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

A French valley with forests so lush it was nicknamed "the Small Amazonia of the Pyrenees."

This French castle is said to have once held the Holy Grail but is now a gorgeous mountaintop ruin.