An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

A beautiful maze marks where three countries meet.

Over time, this castle grew to encompass the entire island.

This series of rope-style bridges brings visitors into a jungle layer that is usually reserved for birds and monkeys.

At nearly 1,000 feet long, this astonishing glass suspension bridge is one of the longest in the world.

A symbol of friendship between the mountainous regions of Switzerland and Bhutan.

Crossing this suspension bridge feels like walking through the sky, a fitting tribute to the head of the Apollo program.

This dizzying span over the ancient Algerian city was once the highest suspension bridge in the world.

This Nigerian nature reserve is home to the longest canopy walkway in Africa.

The land is full of geologic eye candy, such as otherworldly spires, mushroom-shaped hoodoos, and prehistoric fossils.

This extraordinary geological oddity resembles human-made pavement.

Islanders once used this dramatic, otherworldly landscape to hide their cattle from Viking raiders.

An ancient Scottish rock formation said to be the gravesite of a giant remains ensconced in legend and intrigue.

Strange rock formations tower above the river that snakes through this enchanting Icelandic canyon.

A long, winding trek rewards you with a gorge so captivating it inspired a painting in the Tate.

A massive natural rock arch gives the Tuscan mountain its own window to the sky.

After millennia of erosion by sand and churning water this Brazilian valley now looks like a lunar fantasy.

Climb down into the largest sinkhole in Qatar.

Raging waters have created a strange geological site that looks like something off of a progressive rock album cover.

Romania's "Red Ravine" is a little-known natural wonder that bears a resemblance to the Grand Canyon.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

These layered sandstone mountains in China look like they are made of pressed crayons.

A sinkhole and now a swimming hole, too, full of dazzling turquoise water.