Press 1 for knock-knock jokes.

The story behind this beloved toy—named for Theodore Roosevelt and owned by his grandson—is more complicated than you might guess.

The National Park Service’s best-kept secret with views that rival any in D.C.

The tunnel under the Capitol Building where Congress takes out its trash.

An ear-piercing buzzer calls lawmakers to a vote with a series of long and short rings to form coded messages.

A line of blue paint marks the route of the inaugural parade.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

Atop this media building, two hives containing more than 30,000 bees keep the surrounding area vibrant.

The first memorial dedicated solely to the Black troops who fought for the Union.

Look closely and you’ll notice that the color changes a third of the way up the tower.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

The most accurate timepiece in the world.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Largest Roman Catholic church in North America.

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

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

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

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

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

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

A tiny piece of the Moon is embedded in this stained glass masterpiece.

Hanging within this medieval church are the bones of a beast allegedly slain by a fourth-century saint.

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

Two stone columns flank the grand Venice square, but there were supposed to be three.