This giant wooden treehouse within a sprawling garden has its own eatery.

A Perpetually Under construction Park.

An architecturally-focused antique shop.

Funhouse of found art and participatory sculpture.

This abandoned oil depot produces world's longest echo in a manmade structure.

This lab's maddening silence is good for business but bad for sanity.

The neon signs from Las Vegas' past find their final resting place at this unusual graveyard.

If you dial the number in this abandoned office window "Sam Spade’s" secretary will ask you to leave a message.

A unique tribute to the millions of animals who served and died for the British military.

The townhouse where the English poet created some of his most influential work has been preserved in tribute.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

Never actually a tree at all, this spot was the site of London's public hangings for nearly 600 years.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

In the ruins of Glastonbury Abbey lies the alleged resting place of the legendary king.

The oldest residential street in Europe also features an optical illusion.

The remains of a magnificent medieval fortress that was the capital of a vast empire.

In this quiet village, a blue plaque marks the spot where the famous fictional detective retired.

Love is in the air along the small street in Brooklyn.

An eerie, derelict amusement park in Berlin.

This road in the Great Smoky Mountains was supposed to assuage a displaced community, but ended up a $52 million dead end.

The highest point in Belgium is a staircase to nowhere.

Explore the dark underground corridors of this graffiti-covered former military fortification.

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.

Amsterdam's narrowest house facade is a monument to 17th-century tax evasion.