The nearly 200-year-old folly has a secret spiral staircase hidden in one of its pillars.

This dizzying tower was built to better broadcast the 1980 Moscow Olympics.

A factory director designed what was the world's longest suspension footbridge in 1923 so his employees could get to work safely.

A whimsical sensor instrument for Minneapolitans to play on their walks to work.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

A Norwegian-born sculptor created these soaring guardian angels at the entrance to Hoover Dam.

A massive, secret marina for the Nazis' most formidable weapon in the Atlantic.

A bronze statue on a downtown corner honors Minneapolis's favorite career gal.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

In the hinterlands of Serbia's capital, a giant reflective mushroom houses an aeronautical history of the former Yugoslav republic.

Rolling sand dunes of the Sahara... in the middle of the Atlantic Ocean.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

A bit of the Berlin Wall was gifted to the Icelandic capital to commemorate the 25th anniversary of German reunification.

The former Nazi concentration camp stands as a museum to remember this dark chapter in European history.

This stunning concert hall has become a symbol of Iceland's national recovery.

Disused seaplane hangar gets a second life as the jaw-dropping home of Estonia's museum of maritime history.

These abandoned coal mine towers near Sherwood Forest might soon boast the U.K.’s longest zip-line.

This beautiful, historic church looks like something out of a simpler past.

A desert ghost town—occupied for only 12 years—was once home to more than 500 silver mines.

Built in 1911, the Tees Transporter Bridge is one of only six transporter bridges still in operation.

An engraved stone in a village church claims to be the grave of a minuscule folk legend.

This tiny little pool is said to be home to a malicious mermaid named Jenny Greenteeth.

The Midwest's reigning king of surplus stores is full of nothing you need and everything you want.

This Tuscan lake hides a 13th century town that is still visible when the water recedes.