This abandoned sea fort has become an accidental bird sanctuary.

A museum dedicated to exhibiting remarkable outsider art.

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

The world's longest known cave system.

The old building has been restored to its 1907 appearance.

This beloved Baltimore spot features caged dolls, a giant Pez collection, and many, many mannequins.

Washington's iconic carousel has a nice piece of Civil Rights history.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

A merry-go-round that became a rallying point for the early Civil Rights Movement.

A fake 1930s-euro-style hotel with an indoor mini golf course.

Memorial stone for GWAR vocalist, depicted in his iconic costume.

The final resting place of two (or three) presidents, one vampire, and 18,000 Confederate soldiers.

This 29-ton granite ball spins around at the slightest touch thanks to a scientific phenomenon.

This museum devoted to the gothic author holds such interesting ephemera as his socks and walking stick.

The remnants of a wooden-hulled fleet built and abandoned in WWI, now home to a thriving ecosystem.

Designed by Maya Lin, the memorial honors 41 individuals who died fighting for equal rights between 1954 and 1968.

Overlooking the Colorado Convention Center is this giant sculpture made from thousands of triangles.

A small store filled with animal skulls and other curiosities.

A multiversal transit station located right below a highway interchange.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

This modern antique shop is a museum for 1980's Saturday morning cartoon culture.

A pair of gargoyles peer into unsuspecting passengers at Denver’s conspiracy-packed airport.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

A Bibliophile's Dream.