A priceless collection of the Nation's cryptologic history.

A haunting exhibit in a wildlife refuge center highlights threatened species and the conservation efforts needed to save them.

An FDR-era tuberculosis sanatorium has stood abandoned in the suburbs of the U.S. capital for over 30 years.

Two dozen pinball games hidden away inside a most unlikely location.

A relic of FDR's brief foray into utopian urban planning.

A lawn full of retired spacecraft on display at one of NASA's first research labs.

This dig site outside D.C. is known for its exceptionally high density of baby dinosaur fossils and dinosaur eggs.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

Once considered a marvel of engineering, this 107-mile canal played an integral role in building New York City.

A playground inspired by differential calculus dangles from the ceiling of the Liberty Science Center.

A bit of retro transportation flair preserved in the world's largest department store.

Hordes of precariously balanced stone figures crowd the shores of the Hudson River.

Little Red Lighthouse under the George Washington Bridge.

The mummified relics of an American missionary.

The highest point on the island known for buildings that touch the sky.

Take a step into the workshop where Edison and his employees revolutionized the world.

Thomas Edison's home and final resting place also boasts an impressive garage, where some of the earliest electric cars are on display.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

Nikola Tesla's former home contains an homage hidden from plain sight.

The former hotel where Tesla invented the radio.

There are owls with glowing eyes in Herald Square.

The one-time epicenter of American songwriting is now a little remembered Manhattan commercial block.

The one-time office of the architectural firm that ushered in the Gilded Age is now a Club Monaco.

The first museum in the United States dedicated entirely to posters.