The stone marker that Mason and Dixon placed at the eastern end of the famous north-south border they surveyed.

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

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

Built by the patriotic residents of Boonsboro in a single day.

This scenic Maryland park was the site of one of the worst prison camps of the Civil War.

This abandoned sea fort has become an accidental bird sanctuary.

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

The ruins of this long-abandoned unsuccessful gold mine can still be found.

A local farm's collection of unusual structures from a now defunct storybook amusement park.

An eerie, decaying ghost town destined to fade into the forest.

The site where Poe "in great distress, and ... in need of immediate assistance" likely died.

The man who first patented the Ouija board rests in peace beneath a headstone that playfully reflects that achievement.

A short but powerful waterfall resides amid Colorado’s Great Sand Dunes.

The narrow mountain road that carves a path between Florence and Victor is tied to ghost towns and ghost stories.

A dangerous narrow-gauge railroad once traced a route through this striking canyon.

This remote Colorado canyon is home to the second-largest collection of natural arches in the world.

A glimpse of a waterfall is reached by a steel catwalk along a slot canyon located in an Ouray city park.

The site of a defunct mill, that once supplied marble for the construction of the Lincoln Memorial.

A river runs through this remote valley in a very unexpected way.

This razorback ridgeline has doubled as a scenic drive since the early 1900s.

The largest dinosaur trackway in North America is tucked away among this canyon's ghosts and archaeological gems.

This interpretive path lets you get up close and personal with dinosaur bones.

In the middle of a suburban Denver neighborhood is a cave that once provided solace for a prominent Ute chief and his family.

This once-popular otherworldly landscape was formed by one of the largest volcanic eruptions in history.