Once a thriving business district, this former shopping area is now an urban ghost town in the heart of the city.

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

This four-story steel sphere in Maryland was used to test biological weapons.

Proto-CIA agents trained with grenades in the sand traps and fired machine guns from the fairways.

The 72-foot giant escaped confinement in a large patch of mulch only to be reburied in the sandy shores of the Potomac River.

The wooded estate of the Forest Service employee responsible for D.C.’s cherry blossom trees.

The development and impact of electronic media showcased in a picturesque farmhouse in Maryland.

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

Dogs, cats, horses, monkeys, frogs, and fish are laid to rest at the second-oldest pet cemetery in the U.S.

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

Giant acorn-shaped 19th century gazebo from which suburban Washingtonians gazed upon the original "silver" spring.

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.

Once America's tallest structure, now a Baltimore landmark.

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

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.

Live data is transmitted from the Atlantic coast to instantly recreate the ocean waves in this fountain at the NOAA headquarters.

A weathered, American Foursquare-style house originally built for lumber merchant William Wimsatt.

A small brick parlor house and artist's studio located in the wilderness is surrounded by imposing suburban palaces.

Hidden in the forest atop a long, winding driveway is this stately home.

The last of nine massive kilns that produced many of the red bricks for buildings in Washington, D.C. and northern Virginia in the early 20th century.

This little brick tunnel built by Confederate forces was used to conduct surprise attacks on the railroad.

These figures float and flutter in this fountain crafted by famed Swedish sculptor Carl Milles.