Secret North Korean passage discovered below the world's most dangerous border.

Moonbows over Kentucky.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

One of the deepest blue holes in the world.

A building so large that it has its own weather.

Possibly the most beautiful carillon in the world, set atop Iron Mountain in Florida.

A monument celebrating the idea of reaching inaccessible places.

These mansions date back to Chicago's days as a brewer's paradise.

The home of 1.5 million wood letters for printing is still a functioning workshop.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

This "floating railway" is one of the world's oldest monorail systems.

A rare water-powered funicular, it uses a huge tank of water and gravity to do its work.

An Italian hillside ghost town.

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

Caves famous for the dragon-slaying saint who lived there.

Bridge that died in war and was resurected.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

A petite white lighthouse perched on the ancient core of Stromboli Volcano.