A modern ghost town whose inhabitants were driven away by the growth of nuclear power.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

Once the "Eighth Wonder of the World," this iron railroad bridge was decimated by a tornado.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

These beautiful ruins deep in the Pennsylvania woods are thought to have been a ski lodge or a speakeasy, but no one really knows.

A stone arch leads to a cavernous 1930s spring house tucked away in the Pennsylvania woods.

An abandoned stretch of highway, deteriorating next to the operational one.

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.

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

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

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

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.

A historic arena where the Beatles played their first concert in the U.S.

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

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

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

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

Decades before the scandal, this staircase on the river was a literal "water gate."

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

The oldest continuously operating fish market in the United States.

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