Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

A secret climbing tree hides along the side of a Costa Rican road.

An intentionally grounded cargo ship remains half-buried in the sand.

Along a coast that sees the annual migration of humpback whales, a geological formation that takes the shape of a whale’s tail.

The same water that fills a luxury resort’s pools feeds these free hot springs in the rainforest.

The translucent turquoise hue of these natural swimming pools comes from a high concentration of minerals.

In Costa Rica's cloud forest, the roots of a woody ficus create a botanical bridge.

This abandoned hospital is one of the most haunted places in Costa Rica.

One Costa Rican island is so beset by illegal shark poachers that the local rangers have built an entire bridge with their confiscated gear .

Disused penal colony features prisoner artwork, some sketched in human blood.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

Clean, cold drinking water flows from a nondescript pipe in a roadside rock face.

Research missiles and rainbow auroras at the world's largest land-based rocket range.

The stickered marker pinpoints where the only maintained road in the United States crosses into the polar region.

A trading post in the North Pole where children send letters.

A rare chance to get up close and personal with a 13-mile ribbon of ice near downtown Juneau.

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

Breathtakingly blue walls shimmer inside the "Glacier Behind the Town."

Gorgeous cave resemble a winter wonderland.

Now home to a drinking establishment, this building has a macabre history.

The one-time stronghold of the noble Douglas family, now home to ghost sightings and nesting birds.

Ethiopian standing stones featuring remarkably preserved carvings of swords and people.

An ocean in the making, in the Ethiopian desert.

Ethiopia's "smoking mountain" is in one of the hottest regions on the planet and is home to two lava lakes.