The world's longest known cave system.

This defunct, fortress-like prison has been the setting for several movies.

This replica of the Greek structure is in the heart of Nashville.

This massive mural by famed pop-artist Keith Haring was hidden for almost 30 years until its 2018 rediscovery.

A bronze statue dating back as far as 1252, still has remnants of gold on its right cheek from ancient gilding.

The legendary birthplace of the Japanese maneki-neko is dotted with hundreds of lucky beckoning cats.

A 20-meter (65-foot) robot towers over Tokyo Bay.

Tokyo’s only Vaudeville-cuckoo clock–steampunk-Victorian curio cabinet time piece.

After being lost for decades, this striking mural depicting the atomic bomb covers the wall of a busy Tokyo metro station.

A Japanese concept restaurant that feels like a party thrown by the monsters in your closet.

Preserved "bog person" that is over 2,000 years old.

Iron Age "bog person" preserved for over 2,300 years.

A small Denmark town displays a pair of titanic jaw bones as their community symbol.

This colorful artistic feature atop a Danish art gallery allows visitors to stroll through a rainbow.

Digger attempting to hide itself under 300 tons of rubble.

A public display of random paleontology.

Mounds, rune stones, and a 1,000-year-old church, left behind by Denmark's first two kings.

The gilded, masterful astronomical clock will calculate time, dates, and planetary positions for thousands of years to come.

The northernmost point in Denmark is a turbulent sandbar created by two clashing seas.

This sublime architectural marvel is a rare example of an expressionist church.

Hans Christian Andersen for the postmodern world.

A natural wonder in south Denmark.

Vortex-shaped aquarium hosts Europe's largest school of piranhas and other ocean creatures.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.