A 35-foot-tall fork stuck in the ground outside an office building in Missouri.

A big museum full of little worlds.

A collection of oddities including Dr. Kevorkian's suicide device, the Thanatron.

The seamy, underground secrets of Portland's criminal past.

A self-built castle made by a mysterious man.

The oldest original lighthouse in Alaska that was born out of a tragic shipwreck.

A monument commemorating the role of Alaska's native Tlingit guides in the Klondike Gold Rush.

A tiny wilderness cemetery commemorates the deadliest episode of the Klondike Gold Rush.

A classic gold rush hotel can be expected to pick up some ghosts along the way, and the Golden North is no exception.

Colorful boxes placed over the dead are left to rot and crumble.

A trading post in the North Pole where children send letters.

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

Gorgeous cave resemble a winter wonderland.

This whimsical stacked cabin looks like something out of a children's book.

Breathtakingly blue walls shimmer inside the "Glacier Behind the Town."

This ghost town houses the remains of Alabama's old state capital.

The terrified face of Henry Wells is etched on this garret window.

Booker T. Washington's home at the Tuskegee Institute was a gem of splendor.

This architectural triumph is the only Frank Lloyd Wright house in Alabama.

The remains of an idyllic small town built for the film 'Big Fish' still stand around a rundown main street.

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

A crumbling hospital from the 1850s on Roosevelt Island.

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

A 140-year-old castle with underground caves hidden in San Francisco.