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

The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

Where the U.S. government kept its actual treasure, before Fort Knox.

A super-sized promotional trick that is now a D.C. landmark.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

The national park was once a plantation estate.

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

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

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

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

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

The United States Capitol's former columns still stand.

The site of the climactic scene from the classic horror film is now a historic landmark.

Hackney's newest private museum and natural curiosity shop.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

Rainbow-hued local gem in Venice.

An enormous, inside-out glass globe built in 1935.