A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

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.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

The national park was once a plantation estate.

The oldest continuously operating fish market in the United States.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

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

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

There's a crumbling old mansion inside the Smithsonian National Zoo.

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

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

A computer bug so primitive it was an actual insect.

It was once the base for a series of domestic terror attacks.

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

People escaping slavery may have hidden inside a corpse vault.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

The most decorated dog of World War I is preserved in the Smithsonian.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

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

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.

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

The walls of the iconic dome are hollow and have a secret stairway.

A nostalgic bibliographic gem.

Fittingly, America's museum of architecture is itself a magnificently designed old building.