This abandoned sea fort has become an accidental bird sanctuary.

The second tallest railway trestle bridge in America.

Ship skeletons haunt Baltimore's waterways.

A well-preserved Ancestral Puebloan ruin tucked beneath a desert cliff.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

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

An abandoned network of military bunkers and tunnels open for anyone willing to descend into the darkness.

Before it was abandoned and left to rust alongside the road, this riverboat starred in a John Wayne movie.

A mining town, now abandoned, was built in a canyon so narrow that the railroad ran right through the hotel lobby.

Accessible only by boat, this centuries-old island fort never saw troops or combat.

An ill-fated attempt to grow wheat in the sagebrush steppe of northeastern Nevada.

Take a step into the workshop where Edison and his employees revolutionized the world.

Thomas Edison's home and final resting place also boasts an impressive garage, where some of the earliest electric cars are on display.

Memorializing an American tragedy of massive proportions.

The home of possibly the least-loved U.S. president stands as a sort of unpopular Monticello.

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

A tradition unlike any other, this marks the site of the annual Groundhog's Day tradition.

A larger-than-life statue of America's favorite sundae marks the place it was invented.

The universally beloved children's television figure is interred on a high hilltop in one of western Pennsylvania's oldest cemeteries.

Eccentric concrete mansion and museum designed and built by hand from the inside out.

This eerily well-preserved coal town was saved from destruction by a Sean Connery movie.

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

The first partially complete dinosaur skeleton was discovered here, forever changing the world's view of the ruling reptiles.