The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

Ruins of a Carnegie family mansion on Cumberland Island.

An Escher-inspired library dedicated to the wonders of the human mind, yet closed to the public.

A secretive collection featuring objects that were designed specifically for U.S. intelligence operations.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

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

Exotic feline breeding compound and conservation center.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

A beautiful oddities shop crammed with strange and morbid curiosities.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

The ruins of this antebellum sugar plantation are the end result of a Seminole attack during the Florida Wars of 1836.

One of the oldest living oak trees in the Southeast.

A stone arch leads to a cavernous 1930s spring house tucked away in the Pennsylvania woods.

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

Chicago's largest cemetery is full of beautiful Victorian monuments and more than a few ghost stories.

Though its celestial ceiling is impressive, the true star is the vast collection of French books.

A tiny red pebble marks what may be the quietest outdoor spot in the United States.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

Unlock the secrets of the conjuring arts.

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

A French chateau, failed utopian community, odd museum, and Stonehenge replica in rural Washington State.

The lowest point in North America is home to an undrinkable pool surrounded by fields of geometric salt flats.

This brightly made over hotel hides decades of suicide, serial killers, and mysterious deaths.

This family mausoleum is steeped in symbolism and looks more like a fantasy location than a grave.