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

Possibly the oldest living thing in Europe, more likely a pagan survivor.

Nestled amid the peaks and lochs of the Scottish Highlands, this inn and pub has played host to outlaws and ghosts.

Long abandoned underground complex to keep royals safe from a nuclear war that never came.

A pagan tradition of draping trees with rags eerily lives on.

These fantastically named natural pools look like something out of a Scottish myth.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

This dramatic landscape hidden on the Isle of Skye looks as though you've stepped into the magical realm.

This Torino museum honors a soldier who kept the city safe using barrels of exploding gunpowder, losing his life in the process.

Now an entertainment complex, the Lingotto building was once an avant-garde auto factory with a test track on the roof.

When this funny little building went up in the 19th century, most people thought it would simply fall over.

This 18th-century fort surrounded by a moat was used to store gun powder and ammunition, and now sits in the middle of a large part in Dublin.

The oldest public library in Ireland.

One of Ireland's most infamous prisons for rebels including men, women and children.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

The chaotic studio of one of the 20th century's most important artists has been preserved down to the dust.

Dublin's "Dead Zoo" serves as a window to Victorian museum design.

A Serbian church lit by chandeliers made of weapons.

Ride in 1960s style on the private luxury train Marshal Josip Tito used to travel around Yugoslavia.

Extremely famous in his native country, this Cracovian painter is all but unknown beyond Polish borders.

Built to hold the worst of the worst of the Nazi war prisoners.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

Legend says a witch conjured the world's third largest whirlpool to protect Scotland from a nasty pirate.