A plaque commemorates the spot in the Oregon woods where the first-ever Geocache was hidden.

A once-luxurious, now abandoned hotel in the Italian Alps.

A hermit's tiny cell built into the cliffside that saved him in South Pembrokeshire.

This long line of cement defensive wedges is named after the famous chocolate bar for obvious reasons.

An institution dedicated to curiosity, logic, riddles, and Mongolia's long history of puzzles.

What might look like a cliffside sacrificial altar at first glance is actually a stone compass pointing to cities and lighthouses all around the world.

A subterranean shelter remains intact under a busy Paris railway station.

A Japanese train station built around a 700-year-old camphor tree.

The library's graceful rotunda is like a bibliophile's temple.

The ancient mosaics here are considered among the finest in the world, and serve as a stunning record of Greco-Roman daily life.

A 70-foot-deep ice cave formed by lava from Mt. Fuji on the edge of Japan's "Suicide Forest." 

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

An elegant chandelier hangs over this ancient sewer chamber, now open for concerts and public tours.

Featuring one of the most complete and original collections of Presidential memorabilia, this is the site of the last front porch presidential campaigns.

The walls of the iconic dome are hollow and have a secret stairway.

Hundreds of dwarf beeches create an unusual, haunting forest in the north of France.

The cedar tree in Highgate Cemetery earned its title by accident.

This large midwestern cavern features impressive rock formations and an underground waterfall.

Thanks to an acoustic anomaly, this unassuming stone bench has heard one hundred years of secrets.

A century-old hotspot for jazz, frequented by everyone from Charlie Chaplin to Al Capone.

Possibly the world's oldest rug, this Egyptian relic is woven entirely from ancient cat hair and once carried a mummified human foot.

In addition to fine dairy products, the world's most beautiful milk shop also offers a feast for the eyes.

At this California chicken ranch, four bucks will get you 18 eggs and a chorus of dancing animatronic poultry.

A historic London pub with prison cells in the cellar and a "spy room" on the second floor.