An urban laboratory.

This unique historical monument features large concrete spheres designed to resemble fallen stars.

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

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

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

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

The U.S. Army's giant warehouse of war art includes Hitler’s watercolors and Norman Rockwell oil paintings.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.

This former Cold War missile control site played an important role in the creation of GPS.

An out-of-place Air Force radar dome is all that denotes this park as a former missile launch site.

The ruins of this long-abandoned unsuccessful gold mine can still be found.

The neon signs from Las Vegas' past find their final resting place at this unusual graveyard.

A huge musical instrument played by the ocean.

This pre-Revolutionary War grist mill ground corn and flour for soldiers in seven American wars.

In this roadside "community for the small," abandoned toys gain new lives.

A place where the laws of nature seem to have gone completely berserk... but of course haven't.

A curiosity-seeker's paradise set inside a three-story historic school house.

A Tucson museum and performance space full of found-object movable sculptures.

An Arizona museum with a collection of pharmaceutical oddities, including a jar of a gangster's chewed gum.

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

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

This lovely pocket park is one of the most under appreciated in D.C.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.