An ancient system of freshwater caves filled with animal bones, including that of species long-extinct.

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

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

Every equinox this Maya pyramid puts on a spooky ancient light show.

These azure waters were thought to lead to the Mayan Underworld.

Extraordinary sculpture garden created by an eccentric English poet.

An Aztec snake god has taken the material form of an apartment complex.

Started as a kitchen garden, now the second largest botanical garden in the world.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The first declared National Monument in the United States.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

Stroll through a wonderland of stupendous moss-covered trees.

The sign at the garden gate reads: "These Plants Can Kill."

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Enormous lake at the bottom of a unique cave system.

The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

Medicinal spa created with the discharge from a geothermal energy plant.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

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

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

The installation’s official name, “You Who Are Getting Obliterated in the Dancing Swarm of Fireflies,” says it all.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

These fantastically named natural pools look like something out of a Scottish myth.