These World War I shooting range tunnels are now haunted halls of underground graffiti accessed through the roots of a tree.

This secluded walking trail is a hidden gem of a Pittsburgh park.

The remains of a community that was forced to move for a dam that never materialized still rot in this Pennsylvania park.

A train station that was abandoned by the coal industry and was later converted into a cocktail bar.

A mine fire has been burning under the deserted town since 1962, but this church is still going strong.

This palatial botanical garden is home to one of the largest pipe organs ever installed in a private residence, and a piece of Wood's cycad.

Buildings that dynamite couldn't bring down were abandoned because of bathroom issues.

Collection of trolley cars in the woods represent one man's attempt to preserve transportation history.

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

This abandoned Poconos resort is haunted by a history of kitschy romance and a violent fugitive.

The abandoned coal loading dock is a canvas for unsanctioned art.

The graffitied ruins stand hidden within the Pennsylvania woods.

A toxic ghost town sitting atop a massive coal fire.

Over 100 concrete munitions bunkers are all that remain of a Pennsylvanian village seized by the US government.

The site of the first battle of World War II.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

Countless stories attempt to explain Poland's mysterious J-shaped trees.

Tucked behind New Jersey's abandoned Gingerbread Castle lie the eerie ruins of a once-flourishing paper mill.

This huge, disused viaduct is now a crumbling concrete underworld of covered in years of graffiti.

Once the world's largest reinforced concrete structure, this abandoned bridge now beckons urban explorers.

This Boy Scout retreat acted as "Friday the 13th"'s original Camp Crystal Lake.

One of the U.S. Forest Service's only mansions is outfitted with a dinner table for floating food.

Whimsical artist house in the New Jersey woods.

Once in a state of dilapidation, this candy-inspired fortress is now being revived.