A mammoth pair of Civil War artillery guns abandoned out in the forest.

A pre-Industrial Age iron furnace and the site of a nearly-forgotten piece of Black history.

A star fort along the C&O Canal in western Maryland that protected America in three wars.

The "mysteries" of this quintessential roadside oddity were almost destroyed by neglect but were saved by fans of kitschy wonder.

The remains of the iconic train crash from the movie The Fugitive can still be found rusting along the Great Smoky Railroad.

One of the oldest living oak trees in the Southeast.

More than five miles of underground passageways.

This head-spinningly bizarre Depression-era art cave is wall-to-wall quartz and Jesus.

Mile-long cave system near Great Smoky Mountains.

Enormous lake at the bottom of a unique cave system.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

This 1830s store is believed to be the site of Harriet Tubman's first stand.

This futuristically sylvan church is a glass-enclosed marvel of modern architecture.

This labyrinthine resting place of Black American leaders has been reclaimed by nature.

Once a menacing challenge for trailblazers, this trail is now the most scenic drive in Utah.

Across Ring Mountain is a vast collection of Native American petroglyphs unique to the region.

In a 345-million-year-old cave that's 200 feet underground, dinner awaits.

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

A whopping 14,000 copper coins cover this miniature fighter jet.

This museum sits on the site of a decommissioned military communications base.

A cave on the Maryland border where civilians took refuge during the bloodiest battle of the Civil War.

No one's quite sure why there's a metal megaphone bolted on two rocks in the middle of the Mojave Desert.

If there's another drive-through golf-cart bar in a bat-filled cave on top of a mountain, we don't know about it.

Inky sludge oozes to the surface of this beach thanks to a rare natural tar seep.