The world's largest collection of mechanical puzzles is a cornucopia of analog bafflers.

A lesser-known part of the Kinsey Institute is this impressive collection of art, artifacts, and material culture related to human sexuality.

Ornate limestone building now filled with geologic specimens, and more.

A stunning, abandoned limestone quarry in southern Indiana provided the stone to erect the Empire State Building.

A flamboyantly decorated bridge signals diversity and fellowship at the entry to Indianapolis' Broad Ripple Village.

The body of one of the world's most famous outlaws is covered in cement and iron to prevent it from being stolen.

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

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

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

Perhaps the most scandalous statue of America's first president.

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

Washington's iconic carousel has a nice piece of Civil Rights history.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

The "lovely red Vega" of the legendary record-settling pilot.

Seemingly unremarkable items like empty sushi trays, chef hats, and freshness stickers are being preserved so future generations can look back on this beloved cultural import.

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

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

A nostalgic bibliographic gem.

The United States Capitol's former columns still stand.

This private residence was the template for one of the most beloved television homes of all time.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.