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

One of the world's largest model railroads is a mind-boggling achievement.

This historic iron-working village is now a ghost town so immaculate that it looks as though it was recently built.

A unique sculpture park that specializes in the huge and bizarre.

Hidden in plain sight on the Hudson River is an abandoned train station where nature has taken over.

The home and studio of a visionary woodworker now stands as a museum and example of his artistic genius.

Erected in 1697 this Philadelphia bridge is the oldest surviving roadway bridge and perhaps the oldest stone bridge in the United States.

One of the oldest surviving lock houses on the Ohio River.

This abandoned iron furnace was one of the first to use coke—a type of high-carbon fuel—to make iron.

The last remnants of Fort Pitt also hold the distinction of being the oldest structure west of the Allegheny Mountains.

Where the oil industry began.

"Where the ducks walk on fish."

Pittsburgh's literal underground railroad.

This beautiful stone arch bridge wasn't even expected to stand for one day, but people have been crossing it for centuries.

Pennsylvania's highest point is spotted with boulders which were pushed to the surface by nothing but cold.

North America's oldest quarantine facility was built in response to Philadelphia's 1793 yellow fever outbreak.

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

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

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

It would take 35 firetrucks to fill this enormous glacial pothole.

These disused steel furnaces are now haunting ruins that may one day be a national park.

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

A hidden piece of Altoona's railroad history in a long-forgotten abandoned town.

In the bowels of a 19th-century brewery lurks a fine-dining restaurant offering an array of themed feasts.