In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

Washington's iconic carousel has a nice piece of Civil Rights history.

Where the U.S. government kept its actual treasure, before Fort Knox.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

This unique museum cafeteria showcases the history and regional diversity of African American cuisine.

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

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

People escaping slavery may have hidden inside a corpse vault.

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

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

The most accurate timepiece in the world.

This restaurant has been a haven for D.C.'s LGBTQ community since the 1950s.

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

A computer bug so primitive it was an actual insect.

A celebrity from the late Cretaceous period.

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

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

The national park was once a plantation estate.

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

The span is crooked and made from two older recycled bridges.

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