Built in 1815, the stabilized ruins of the grist mill and sawmill are now gated, but interpretive displays on the features and functions of the mill preserve its history.

The hidden ruins of a mill that is linked to an attempt to assassinate the vice president of the United States.

Unannounced visitors are now welcome at the site of the largest Prohibition-era bootlegging operation in the region.

Remains of a historic fountain that was mysteriously lost in the demolition of a D.C. traffic circle.

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

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

This ruined quarry once produced the distinctive red sandstone used for construction projects in Washington, D.C.

Once part of a dam servicing an early 19th century grist mill, the tucked-way falls are a tricky-to-find urban oasis.

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

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

This simple convenience store sits on the location where the Ouija board was named—and has a plaque to prove it.

After hundreds of years of settlement, this once-bustling fishing village sunk into the Chesapeake Bay.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

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

Despite violent work crews and massive delays this abandoned canal tunnel was built to last into the modern day.

An FDR-era tuberculosis sanatorium has stood abandoned in the suburbs of the U.S. capital for over 30 years.

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

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

An intricately designed junk art house with four extravagant junk art cars hidden in the suburbs.

A priceless collection of the Nation's cryptologic history.

An astounding collection of medical specimens, including bits of President Lincoln.

A hidden alley in urban Baltimore is a haven for graffiti artists.

Bizarre Cavern.

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