Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

A huge musical instrument played by the ocean.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

An original apothecary from 1792.

The highest point in Virginia can only be reached by passing through ponies and flowers.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Exact replica of the ancient monument, but much, much lighter.

Paranormal investigators claim this abandoned asylum is the most haunted spot in the eastern U.S.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

Outsider art meets paleontology at this roadside reptile repository.

The remains of a failed attempt at medieval nerdery are hidden deep in the woods of Virginia.

This maze-like slot canyon is a unique gem within an already fascinating geological area.

A collection of artifacts from Maryland's maritime past.

The shelves in the back of this thrift store are devoted to saving, not selling, retro tech.

Once the center of a thriving early Black community called Martinsburg.

This mighty white oak in Bethesda survived both the American Revolution and the construction of Washington D.C.'s metro red line.

Dating to 1793, this is the oldest building in Poolesville.

A rural colonial settlement that contains the remains of a store and cooper.

One of the oldest standing structures in Montgomery County, Maryland.

One of the oldest active carousels in the country—but it might be missed by all but the keenest-eyed boardwalk strollers.

Surrounded by traditional homes, this Tolkien-esque dwelling stands out on a quiet street in suburban Maryland.

Maryland's first (and last standing) toll house on America's first federal road established the state as the "Gateway to the West."

This suburban house is made of dirt, and almost sparked a revolution in home construction.

The antique hotel still has a jail in the basement, though the cockfighting ring is long gone.