Seemingly unremarkable items like empty sushi trays, chef hats, and freshness stickers are being preserved so future generations can look back on this beloved cultural import.

A celebrity from the late Cretaceous period.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

A computer bug so primitive it was an actual insect.

A super-sized promotional trick that is now a D.C. landmark.

An Industrial Revolution-era public work that purified water using nothing but sand.

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

The oldest continuously operating fish market in the United States.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

There’s a hidden military meme engraved on the World War II Memorial.

People escaping slavery may have hidden inside a corpse vault.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

A nostalgic bibliographic gem.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

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.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

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

A derelict bit of transportation infrastructure hidden in the woods.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

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

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

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