At the center of this cemetery stands a 2,000-year-old burial mound of the Adena culture.

The mounds at this site were reconstructed with the help of archaeologists and historians.

The internal railway of one of the biggest steel plants in America has been transformed into a linear park with unique industrial views.

A small cave hidden deep within the Jenny Jump State Forest.

Local lore claims this park is named after a young woman who jumped off a cliff.

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

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

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

The largest earthwork effigy in the world.

A slab of sandstone covered with mysterious 1,000-year-old rock carvings from a vanished North American culture.

This national landmark is also home to a massive treehouse.

A monument to an Irish secret society thought to be responsible for a string of violent attacks in Pennsylvania coal mines.

Outside a small brewery, a Gothic fountain that once provided water to thirsty horses.

The only geyser in the state of Pennsylvania is caused by pressure from an abandoned coal mine outside of the ghost town Centralia.

A eight-foot-tall statue resides in the heart of Pennsylvania anthracite coal country.

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

A toxic ghost town sitting atop a massive coal fire.

An underground blaze turned this village into a ghost town.

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

A retired firefighter created this contraption so he and his family wouldn't die if accidentally buried alive.

According to local myth this cemetery is half evil spirits, half good—split down the middle.

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

Dedicated to the art and science of glass in equal measure, this space is as much laboratory as museum.

This unique creation was made by the largest manufacturer of Christmas bulbs in 1946 to honor those returning from World War II.