This abandoned urban warfare facility is a dream come true for airsoft and paintball enthusiasts.

Walking through this narrow gorge will make you feel like you've fallen into a fairytale landscape.

This Swedish sculpture park is a unique combination of ancient ruins and modern art.

Sweden's southernmost prehistoric rock art is hidden just outside Gothenburg.

This castle ruin in the middle of nowhere is a gem for wildlife enthusiasts.

Rare recess caves fill this unbelievably beautiful Ohio park.

Believed to be the country's tallest waterfall, the Njupeskär is actually much smaller.

This Swedish astronomical clock was in storage for almost a century before its glorious workings were put on display once more.

The marker that allows students all over the world to be late for class.

The stunningly blue waters of these beautiful caves also have a violent past.

These artificial caves crafted by ancient Romans were elaborate fish farms for moray eels.

Home of a 28-foot tall stalagmite known as the War Club.

The oldest arched-covered bridge in Virginia has truly withstood the test of time.

This brick-lined pedestrian walkway was once a railway tunnel used during the Civil War.

Walk or bike along a narrow strip of Belgium sandwiched by German territory.

Hikers can still stroll beneath the long conveyer of this abandoned mining facility hidden in a West Virginia river gorge.

The only geyser in the state of Pennsylvania is caused by pressure from an abandoned coal mine outside of the ghost town Centralia.

Accessible only by train, the beauty of Agawa Canyon Wilderness Park is worth the journey.

Underwater art project will double as a massive artificial coral reef to help regenerate the damaged ecosystem.

Take a dip beneath the stalactites in this amazing cenote.

This popular cave pool is truly magical, despite the crowds.

The walls of a colonial-era fort encircle a small, tropical assortment of plant life.

Found down a long dirt road, a sacred Mexican cenote and 18th-century hacienda remain hidden.

Clap your hands at the base of the pyramid, and the song of a sacred Mayan bird will echo through the air.