The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

Elevated freight railway turned wildly successful urban park.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

A bizarre house filled with an astounding array of collections.

The legendary building that needed ghostly approval before being built.

Remants of foundations, streets, and streetcar tracks inhabit the cliffs where a landslide occurred in 1929.

Dramatic river bend surrounds a natural red-rocked pedestal.

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

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

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

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

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

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

Rippling sand dunes frozen in the Arizona rock.

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

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.

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

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

The oldest dim sum restaurant in the United States is a nostalgic jewel.

A museum befitting the city responsible for supplying the majority of the world's LSD.

Furniture tries to escape an abandoned building in San Francisco.