A derelict bit of transportation infrastructure hidden in the woods.

This simple stone memorial remembers a secret, Geneva Convention-defying interrogation base from WWII.

The school tested mustard gas for the U.S. Army during World War I.

The romance of early commercial flight still fills this Art Deco destination.

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

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

Look closely and you’ll notice that the color changes a third of the way up the tower.

Despite time, colonization, and the brutal New Mexican heat, these Pueblo ruins still stand.

A sprawling collection of over 106,000 toys from around the world.

These Pre-Columbian petroglyphs contain representations of birds, deer, hunters, and even some early Native flute players.

This southwest-styled home in Santa Fe claims to be the oldest house in America thanks to an ancient bit of foundation.

Wedding chapel's mysterious spiral staircase said to be miraculously constructed.

This innocuous New Mexico storefront was once the secret jump-off spot for Manhattan Project scientists.

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

This pun was simply waiting to come to life, and one defense contractor made it so.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

Once America's tallest structure, now a Baltimore landmark.

It's not hard to see why the historic Peabody Conservatory of Music's library has been described as a "cathedral of books."

This simple convenience store sits on the location where the Ouija board was named—and has a plaque to prove it.

The design of this historic domed church was influenced by Thomas Jefferson and intended as a statement of religious freedom.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

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

The bridge's highly-contested plaque (once again) honors Confederate President Jefferson Davis.