One of the steepest streets in the United States makes an intriguing challenge for cyclists.

A stone arch leads to a cavernous 1930s spring house tucked away in the Pennsylvania woods.

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

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

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

An abandoned stretch of highway, deteriorating next to the operational one.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

Where America's first doomsday cult awaited the end of the world.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

Mysterious rocks that ring musically when struck.

An abandoned cemetery lies in ruins as the surrounding forest swallows it whole.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

Remnants of a storybook amusement park hidden behind a strip mall.

The childhood home of the Sultan of Swat is just a line drive away from Oriole Park at Camden Yards.

An eerie, abandoned military base engulfed by nature and graffiti is now home to a local park.

A swimming hole in the historic industrial quarry that supplied the marble for the Baltimore Washington Monument.

An isolated island home to one of the oldest English-speaking communities in the region and Maryland's state dessert.

The rooster who crossed the road lives on forever in Takoma Park, Maryland.

Three abandoned missile silos are hiding in plain sight behind a suburban development in Maryland.

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

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

This one-room cabin where the young colonel slept during the French and Indian War.

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

Politicians, bureaucrats, and military officers gathered in this field near the Capitol to settle their disputes with blood.