This stunning natural double arch, the largest in the Alps, went undiscovered until 2005.

The largest natural travertine bridge in the world is nestled in a small canyon in central Arizona.

Built in just a little over a week this preserved bunker was created to protect our most attractive POTUS while he was on vacation.

The world's second largest single-dish radio telescope, once used to contact E.T.

This trio of Dominican cave lakes comprise a colorful biosphere of natural life.

Hundreds of pieces of ancient Taíno art cover the walls of this Caribbean cave system.

The first hospital in the New World.

Massive sinkholes on a mountain in one of the most remote places in Venezuela.

This striking, two-toned confluence of rivers is visible from space.

A beautiful opera house in the heart of Amazonia has recently restarted performances after a 90-year hiatus.

This "floating island" plateau sits 7,671 feet above the forest floor.

An abandoned colonial French prison notorious for its hellish conditions.

A faux desert landscape in the middle of the jungle that sprouts oases during the rainy season.

Unusual rock formations eroded into a landscape of stone beasts.

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

These termites have an large and deadly abode—impressive by day, dazzling by night.

A series of waterfalls so massive they straddle the border of Argentina and Brazil.

These spectacular ruins were built by Spanish padres in the 17th century.

Mysterious and ancient carved standing stones.

A toxic lake near a volcanic caldera that is home to flamingos and other life.

What was once a unique system of urban elevators is turning into a mechanical ruin.

A fantastical group of cliffside stairways, bridges, and twisting paths carved out of stone provide a surreal coastal hike.

Massive rock sculptures formed during the time of the dinosaurs still stand undisturbed.

Isolated atop this Balinese sea crag is a lovely Hindu temple that is said to be guarded by sea snakes.