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

Dramatic river bend surrounds a natural red-rocked pedestal.

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

The sound of swaying stalks in this stunning grove has been named a governmentally recognized sound.

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

World's first "penitentiary," meant to be humane, drove men insane.

Rippling sand dunes frozen in the Arizona rock.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Since the 1700s, this old barrel has acted as a post box that relies on the kindness of travelers.

Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.

An Inca spa, military outpost or maybe… both?

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

These steeply terraced ruins are a stop along the Inca Trail to Machu Picchu.

The stones of this Incan wall complex fit together so well you couldn't fit a piece of paper between some of them.

This Peruvian canyon is filled with geometric salt pools that have been being harvested since the Incan empire.

If you’ve ever seen a picture of Machu Picchu, then you’ve seen a picture of Huayna Picchu—you just didn’t realize it.

Preserved Inca city and site of the last Inca stronghold against the Spanish conquistadors.

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

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

Museum of Fijian history, including its former tradition of cannibalism.

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

A hidden treasure of an abandoned city lies deep in the jungles of Campeche, Mexico.

The last four extravagant street signs of London's historic banking street.