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

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

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

The whole world in one water tank.

This abandoned Victorian-style house was built in 1884.

A Civil War Museum with some notable medical antiques.

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

One of the oldest Catholic churches in the U.S., situated just east of Gettysburg.

A labor of love built by local hang-gliding enthusiasts, this ideal launch spot was outlawed by the authorities and has since been largely abandoned.

The Cold War-era "underground Pentagon" is a sprawling subterranean hideaway for the Defense Department.

A diorama of the Civil War, fought by cats.

This recreation of a 19th-century dime museum is full of oddities.

The beloved, war-tested mascot of a Union regiment graces their battlefield monument.

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

Built by the patriotic residents of Boonsboro in a single day.

Bizarre Cavern.

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

A monument marks the location of the first successful steamboat demonstration.

Endless rows of boxes of paper records line the hallways of the archaic federal facility where guns are traced.

A giant time capsule not scheduled to be cored until 2040.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

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

Berkeley Hot Springs presents to you "the only outdoor monument to presidential bathing."

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