This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

The only structure left with direct ties to the Salem witchcraft trials of 1692.

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

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

An exquisite tunnel of cascading flowers.

The world's only museum devoted to the wonders of fluorescence.

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

A theme park that suffered massive flooding during Katrina was abandoned, and now proves irresistible to trespassing explorers.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.

An enormous, inside-out glass globe built in 1935.

An abandoned cemetery lies in ruins as the surrounding forest swallows it whole.

These old stone ruins in the Oregon wilderness were once bathrooms and are steeped in legends of murder.

The neon signs from Las Vegas' past find their final resting place at this unusual graveyard.

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

On the Oregon coast there is a natural hole that seems to be draining the sea.

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

An eerie, derelict amusement park in Berlin.

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

Rippling sand dunes frozen in the Arizona rock.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

An artsy hidden staircase leads to breathtaking views of San Francisco.

A psychedelic labyrinth on the San Francisco bay.