Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.

The earliest known map to show America, discovered by accident at a Paris bookshop.

Built to power trains, the engines in this building provided the entire city of Madrid with electricity during the Spanish Civil War.

Things seem to roll, flow and run uphill on this short patch of road near Ariccia, Italy.

This ancient trail climbs the mountain where a Latin League cult worshipped Jupiter, its main deity.

This famous city eluded concrete detection until the early 2000's.

This eatery re-creates dishes from the Ottoman Empire so you can dine like a sultan.

The most metal church of all time was built in record time because of an international, pious pissing contest.

The classic Atari game's iconic aliens have invaded downtown San Diego.

This museum is dedicated to the little known ancient Roman history of Vienna.

The final resting place for the remains of 143 Habsburg royalty.

A small museum filled with over 1,000 clocks, and one particular clock calibrated to run until the year 9999.

Legends surround an ancient tree trunk riddled with nails for good luck.

A silly medieval mural preserved on the side of a Viennese house.

Once home to one of the oldest banks in the world, this building is also where Marco Polo's famous travelogue was written.

The final resting place of the world's first nuclear reactor.

The names Lúthien and Beren can be found inscribed on the shared grave of the famous writer and his beloved wife and muse.

Did he come up with a theory of cosmic-ray showers while sitting in this bath?

Once the world's biggest telescope, it was later used as a coat hanger by a famous Dutch astronomer.

The last of Amsterdam's original sea level markers remaining in place.

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

This large copper bolt represents the benchmark for measuring sea levels in most of Europe.

Europe's official "zero-level," the equator of elevation.

Tucked in the back of a flower shop, its collection details the fascinating history of the Netherlands's iconic symbol.