Thousands of Mexican Free-Tailed Bats soar around an abandoned storm drain at sunset each summer.

The artist James Turrell is repurposing an extinct volcano crater as an observatory to experience the cosmos.

An arsenic-filled pool in the Grand Canyon takes on the appearance of a giant, overflowing pumpkin.

Eons ago, a rushing lava river formed this pristine passage through solid rock.

See massive fossils that are over 200 million years old in northeastern Arizona.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

Dramatic river bend surrounds a natural red-rocked pedestal.

Most-visited and most-photographed slot canyon in the American Southwest.

Rippling sand dunes frozen in the Arizona rock.

Erected in 1803, it is the first astronomical observatory that was built in the Americas.

A self-taught astronomer fell in love with the stars and built his own observatory in Colombia.

The enormous appendage offers spectacular views of Colombia's Huila Department.

This whimsical home made entirely from clay is basically a giant piece of pottery.

Unparalleled stargazing, one of Colombia's best observatories, and a swimming pool can all be found in the middle of this ancient tropical forest.

An explosion of natural color known as "the river that ran away from paradise."

The largest dam in the world and the site of a potential disaster.

This striking icon of the disputed Republic of Artsakh caused a stir at a Eurovision Song Contest.

Mysterious hillside with a continuously burning natural fire.

Home to nearly a third of the world's mud volcanoes, Azerbaijan is home to a messy, bubbling, and sometimes explosive landscape.

This cavernous swimming spot doubles as a home to the largest known colony of bats in Central Asia.

A cemetery with goat-horn bedecked gravestones.

This famed Silk Road oasis was one of the largest cities in the world before it was destroyed by a Mongol horde.

A cave covered with bizarre stalactites of cloth.