This tiny river island switches sovereignty every six months as part of a rare, centuries-old agreement.

It's 2 billion years old!

When you can afford only half a road, you build only half a road.

In the town of Åtvidaberg, the midday sun sets off a loud cannon boom.

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

These steeply terraced ruins are a stop along the Inca Trail to Machu Picchu.

A tongue-in-cheek arcade where the games are based on everyday life.

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

The only place in America where anyone who wants can shovel coal aboard an antique train.

A fairytale Gothic castle steeped in Nazi treasure conspiracy theories.

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

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

An abandoned bus station transformed into a museum dedicated to the history of Greyhound Lines, in the place where it all began.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

Every year model trains zip through a miniature New York City that's now 150 landmarks strong.

There are hundreds of secret WWII bases hidden in British forests. Built to fight a Nazi invasion, they remained unknown for decades.

These towering spires and glowing walls are carefully crafted from hundreds of thousands of icicles.

A second generation sun-powered marvel lights up the night.

One man's fascination with Turkey led to this backyard mini-city.

A remarkable range of flora and fauna are represented in this Dominican nature preserve.

The "Skinny House" is made from scrap, salvage, and a neighbor’s kindness.

An unrecognized micronation declared by Greenpeace to protect the glaciers of Chile.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.