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

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

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

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

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

This grand gothic brewery has been pumping out suds for over a hundred years.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

Home to items never before seen by the public.

The site of the climactic scene from the classic horror film is now a historic landmark.

The last of Philadelphia's wood-paved streets is now a landmark of terrible engineering.

Century-old shop, specializing in Occult products.

A tour de force of a fountain, memorializing a man who loved fountains more than anything else.

This forgotten building was one of the few Philadelphia-area breweries to survive Prohibition.

A daily replay of the experiment that proved the rotation of the Earth.

One of the oldest of its kind.

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

An Irish Memorial commemorating those who perished due to potato blight.

Current docking place of the SS United States, the fastest transatlantic ocean liner.

This elaborate towering structure was once famed for its revolutionary height.

Yo, Adrian!

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

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