This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

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

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

Behind an abandoned storefront is an example of pioneering 1930s gas station architecture.

This bridge over D.C.'s Rock Creek Park is sometimes called the "Buffalo Bridge" because of its four buffalo sculptures, which were cast from a single piece of bronze.

A terrace reminiscent of Rome's Spanish Steps is tucked away in a little park in Washington, D.C.

Singapore's landscaping project is home to 18 incredible Supertrees.

Holy Hindu shrine in an enormous, monkey-filled limestone cavern.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

Inside this museum, the history of the Walt Disney Family empire is on full display.

A monument to the love people have for their pets.

This lighthouse has been guiding shipping into the Golden Gate since before the American Civil War.

Internationally-recognized arts center housed in a century-old former military barracks.

Ride on a fully-restored Nike nuclear-tipped missile elevator from the Cold War.

Concrete strongholds stand guard over the Golden Gate.

Frank Lloyd Wright died a year before construction on his largest public project even began.

Beneath the southern end of the Golden Gate Bridge is the “Gibraltar of the West Coast,” a fort built to protect the San Francisco Bay from naval attack.

Social saloon from a scrapped trans-Pacific 19th century steamer.

An abandoned, unfinished mansion on grounds strewn with lava rocks.