A much-maligned monument to teetotalism.

An unassuming, powerful monument north of the U.S. Capitol bears witness to the resilience of Japanese Americans during a time of grave injustice.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

A historic ruin just 20 feet away from a busy highway onramp.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

A Spiritualist house of worship where believers communicate with the dead in the spirit world.

The house where John Wilkes Booth conspired with his co-conspirators.

A derelict bit of transportation infrastructure hidden in the woods.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

Underneath this small church are 15,000 bones, arranged by an obsessive academic.