The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

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

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

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

An unassuming, powerful monument north of the U.S. Capitol bears witness to the resilience of Japanese Americans during a time of grave injustice.

The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

Sit where JFK proposed to Jackie or where Nixon dined on meatloaf at this storied pub.

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

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

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

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

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

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

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

A bizarre roadside attraction and the first instance of miniature golf in the world.

St. Augustine's record-setting narrow street was designed to protect against pirates.

In this case, 'zero' marks the spot where the iconic Old Spanish Trail ends.

Intertwined, interspecies trees which locals believe can grant boons to lovers.

An 18th-century Spanish watchtower made entirely of seashell and concrete.

Two men built this castle on the Florida coast as an artistic “landscape sculpture.”

A tribute to Ponce de Leon's supposed quest for eternal youth.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

This historic hotel on Bathhouse Row in Hot Springs National Park has a storied history of gangsters and baseball greats.