Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

This French ghost town from World War II has been left as a memorial to German atrocities during World War II.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

An all-American grocery store in Paris sells U.S. "cuisine" like Pop-Tarts and Heinz ketchup to homesick ex-pats.

The historic Masonic Lodge in which the first-ever female Mason was initiated.

What looks like a normal building is really a hollow facade hiding a subway vent.

One of the oldest masonic museums in Paris.

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

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

Abandoned railway line circling the city of Paris.

The very center of Paris is surrounded by a bevy of strange good luck rituals.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

Large military radio station without transmitting towers.

The largest cave in Northern Europe.

This abandoned mining village was predicted to resist decay longer than any other modern human settlement.

A Viking-style brewpub named for a Norse sea giant, in the heart of fjord country.

For six months of the year, three giant mirrors direct a pool of sunshine onto this otherwise occluded town.

Longest road tunnel in the world features an air treatment plant and the illusion of daylight.

Home to three historic ships from the age of Vikings.

A fantastic reconstruction of a 10th-century Viking longhouse.

Travel deep inside of Europe's second largest glacier in the world's largest man-made ice cave.

A trio of hidden hot tubs takes advantage of Iceland's natural geothermal vents.

This replica Viking village was created for a film that was never shot and is now open to visitors.

This hobbit-y little hot spring may be the oldest spring used by humans in all of Iceland.