A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

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

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

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

Rippling sand dunes frozen in the Arizona rock.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

World's largest collection of serial killer artwork and other macabre exhibits.

A psychedelic labyrinth on the San Francisco bay.

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

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

A huge musical instrument played by the ocean.

This little museum in the town where zombies were born celebrates the living dead.

The most decorated dog of World War I is preserved in the Smithsonian.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

People escaping slavery may have hidden inside a corpse vault.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

A historic cemetery filled with quirky faux wood art and unique tombstones.

Current docking place of the SS United States, the fastest transatlantic ocean liner.

This little-known Revolutionary War fort is supposedly haunted by the ghosts of its past.