The enigmatic and seldom visited ruins of a Mayan city-state.

A flooded Mexican cave that hides a river beneath the water.

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

An emerald-green grotto just a short trip from Austin.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

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

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

An elaborate Mayan city shrouded in alien conspiracy revealed the tomb of Pacal the Great.

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

An extraordinary natural landscape of mountains, waterfalls, and rocky cliffs riddled with tunnels.

The concrete shell of an industry giant remains as a playground for graffiti artists, auto scrappers, and paintball warriors.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

Lake within a lake.

Bohemian paradise covered in majestic forests.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

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

"Only the devil could play golf here."

Each year these high desert hills are absolutely covered with poppy flowers in a surreal show of nature.

A mysterious and endangered parasitic herb from the California desert.

Towering basalt columns, a creation of fire and ice.