World War II-era bunkers are hidden under the beaches of this picturesque park, which is still scattered with wartime watchtowers.

The historic home still shows the scars from a little run-in with the British in 1813.

Home of the only civilian casualty at the Battle of Gettysburg.

Sail through this subterranean show cave that is home to a legend that would go on to name nearly everything around it.

A planned settlement in Pennsylvania once housed the aristocratic refugees of the French Revolution.

Both the building and blades of this reconstructed 19th-century windmill can turn in a breeze.

Captain John Smith thought these cliffs were amazing in 1608 but sharks thought so 20 million years before him.

A small museum along the Susquehanna River is home to a rich collection of Native American artifacts.

Although built to generate electricity for Marylanders, this dam has become an all-you-can-eat buffet for American bald eagles.

This historic lighthouse was well known for the large number of women who served as its keeper.

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.

This collection honors the iconic, and proudly American lighter that just won't quit.

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

Contrary to what one might expect, ice forms inside this small cavern during the summer and melts during the winter.

This lush forest valley was once mined for lumber to the extent that it was once nicknamed "The Pennsylvania Desert."

"Dark Sky Park" is heaven on Earth for astronomers, one of the rare U.S. locations with no artificial light pollution.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

A monument celebrating the idea of reaching inaccessible places.

Grand architectural relics gain a new life in this Pennsylvania warehouse.

The train collection of an eccentric New England seafood mogul is now a National Historical Site.

The first of Lancaster's "rural cemeteries."

Don't get it twisted: This is the oldest pretzel bakery in the United States.

What looks like a simple quaint estate in rural Pennsylvania was in the 18th century home to a small monastic community.