A derelict bit of transportation infrastructure hidden in the woods.

This abandoned prison castle has become an imposing gallery of graffiti art.

A bigger-than-life pun that has become a beacon of altruism.

Julia Morgan's Moorish-Gothic labyrinth of fountains, trees, natural light and Oakland's notable dead.

Twice a year, visitors can tour the desolate site that birthed the Atomic Age.

Friction between grains of sand cause a curious "singing" sound.

The only remnant of a small mining town is an abandoned railroad tunnel that is steeped in ghostly lore.

San Franciscans leave gifts and messages for the magical beings that live behind the tiny, mysterious door installed on a tree in Golden Gate Park.

A beautiful final resting place for some of the noteworthy deceased.

This bridge is haunted by the ghost of a distraught mother.

Abandoned concert venue legendary for its rock counterculture.

The unbelievably opulent home built for an infamous newspaperman.

A modern ghost town whose inhabitants were driven away by the growth of nuclear power.

This crumbling UFO is one of only a few remaining "moveable ski chalets" of its kind.

This Colorado hiking trail provides a small gold mine of abandoned gold mines.

The site of the first couple's first kiss is commemorated by the most adorable presidential monument ever.

Prison made famous by The Shawshank Redemption has been out of commission since 1990.

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

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

These beautiful ruins deep in the Pennsylvania woods are thought to have been a ski lodge or a speakeasy, but no one really knows.

Made of giant chains and hung with shackles, this iron cross honors those unknowns who perished under American slavery.

The oldest house in Manhattan is now a museum that remembers the home's sordid history of scandals, vice-presidents, and ghosts.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

The abandoned personal amusement park of the King of Pop.