In the middle of downtown Brooklyn lies a 165 year old secret hidden right below the surface (closed to the public indefinitely).

Ride the subways of yesteryear.

Just your average Marie Antoinette–themed speakeasy in an abandoned 19th-century subway tunnel.

This innocent-looking townhome is actually a subway exit.

Before online banking and smartphone apps, there was "commuter banking" in the subway in Downtown Brooklyn.

Love is in the air along the small street in Brooklyn.

The Underground Railroad passed right through this historic Brooklyn Heights church.

This impressive mansion in Vinegar Hill has some mysterious details in its architecture.

Walk into the 19th century without leaving Brooklyn.

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

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

A state park that once served as an important river crossing, and now offers protected lands for endangered plants and animals.

Home of the physician who set the leg of John Wilkes Booth after the Lincoln assassination.

This scenic Maryland park was the site of one of the worst prison camps of the Civil War.

Captain John Smith thought these cliffs were amazing in 1608 but sharks thought so 20 million years before him.

Its diverse collection of computers and technology spans the ages.

A swimming hole in the historic industrial quarry that supplied the marble for the Baltimore Washington Monument.

A clone of a cloned tree that was so important it allegedly had its own guards.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

A tribute to the pop culture icon overlooks this Washington D.C. intersection.

A public art jibe at one of the United States’ oldest and longest-serving senators.

The oldest house in Washington, D.C. wasn't originally constructed in the nation's capital.

The towering figures were created from the cemetery's fallen old-growth trees.

An 18-mile-long tunnel for sewage waste will soon wind within the bowels of Washington, D.C.