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

This golfball sized platinum iridium cylinder is the official starting point for all national weight calibrations

A priceless collection of the Nation's cryptologic history.

Tiny observatory made big contributions to the study of the Earth's motion.

This abandoned asylum was once a state of the art facility before devolving into one of the most deadly mental institutions in American history.

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

Collecting 700 years of mechanical death-dealing, the NRA's sprawling gun museum is a revealing testament to the American obsession with armament.

Walk a trail through a historic Quaker town that outlawed slavery in 1777 and was a major waypoint on the Underground Railroad.

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

A haunting exhibit in a wildlife refuge center highlights threatened species and the conservation efforts needed to save them.

The shelves in the back of this thrift store are devoted to saving, not selling, retro tech.

This dig site outside D.C. is known for its exceptionally high density of baby dinosaur fossils and dinosaur eggs.

A 14-foot monument marks the resting place of two of the town's earliest residents—and one unknown soldier.

The final resting place of the tragic king and queen of the Jazz Age is tucked away in a small Maryland graveyard.

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

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

Volcanic stone sentinels stand watch at a Korean Bell Garden in Virginia.

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

This fort down the Potomac from Washington, D.C. was once the only defensive fort protecting the capital.

This simple stone memorial remembers a secret, Geneva Convention-defying interrogation base from WWII.

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

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

A lawn full of retired spacecraft on display at one of NASA's first research labs.

A double agent hid information for the Soviet Union beneath this bridge for more than 20 years.