One of the last Jazz Age "Wonder Theaters" in New York City.

The original toys that inspired the beloved children's stories are on display at the New York Public Library.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Elevated freight railway turned wildly successful urban park.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

This tiny church near Sleepy Hollow contains Henri Matisse's last work, a rose window, and nine windows by Marc Chagall.

The antique hotel still has a jail in the basement, though the cockfighting ring is long gone.

Washed out by the Johnstown Flood in 1889, the surviving portion of the original two-span bridge now resides at Fishing Creek.

The smallest covered bridge in Maryland.

The Cold War-era "underground Pentagon" is a sprawling subterranean hideaway for the Defense Department.

A pre-Industrial Age iron furnace and the site of a nearly-forgotten piece of Black history.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

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

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

An Industrial Revolution-era public work that purified water using nothing but sand.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

A derelict bit of transportation infrastructure hidden in the woods.

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.