Crammed into a Baltimore row house is an oddities shop that sells everything from skulls to dead insects.

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

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

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

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

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

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

The most accurate timepiece in the world.

Perhaps the most scandalous statue of America's first president.

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

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

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

This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

A computer bug so primitive it was an actual insect.

A brass plaque dedicated to a convicted cannibal hangs in the National Press Club, and that's not even the craziest part of the story.

Largest Roman Catholic church in North America.

Home to a vast and influential collection of Shakespeareana.

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

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

When it opened during the final years of the embargo, all the drinks and cigars were free.

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