A retrofuturistic art installation in the Pittsburgh Airport.

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

There’s a special club house at the top for the bell ringers.

The national park was once a plantation estate.

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

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

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

The U.S. Fish Commission’s effort to mass produce carp.

An overlooked memorial honoring the local Washington residents who died in World War I.

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

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

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

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

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

The 72-foot giant escaped confinement in a large patch of mulch only to be reburied in the sandy shores of the Potomac River.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

The rogue roots are gradually consuming some of the historic marble grave markers.

The naval commander’s proudest moment in battle is memorialized in this unique tomb at Arlington Cemetery.

The remains of a historic plantation nestled in between a parking lot and the rental car return at Reagan National Airport.

The romance of early commercial flight still fills this Art Deco destination.

This isn't your average roadway—it's actually a National Park and a transportation pioneer.

A former major munitions plant that has been converted into a sprawling art space.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.