This propitious plastic porcine has been petitioning park visitors to pick up after themselves for more than 50 years.

One of the earliest and best-preserved buildings in Charles County, Maryland.

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

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

This bell is one of the last remnants of the lost city of Triadelphia.

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

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.

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

A historic cemetery with unique artwork, a Civil War fort, and also happens to be the site of the Battle of Bladensburg.

The headquarters of the Audubon Naturalist Society is a small slice of heaven for nature lovers.

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

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

At this former Prohibition speakeasy, electric birds signaled the arrival of hooch.

A Maryland museum dedicated to Black history, housed in a historic church.

The U.S. government built the million-pound stack of steel during the Space Race.

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.

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

A suburban museum tells the story of a historic transportation network and even provides rides in antique trolley cars.

One of the only memorials dedicated to journalists who died in combat.

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

A benevolent, 16-foot-tall river dragon lives on a suburban lawn.

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

Historic home of America's sweetheart sharpshooter, Annie Oakley.