Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

The fountains of the U.S. Navy Memorial are annually salted with water from the Seven Seas as part of a nautical ritual.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

A much-maligned monument to teetotalism.

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

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A historic ruin just 20 feet away from a busy highway onramp.

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

The most decorated dog of World War I is preserved in the Smithsonian.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

The "3rd largest" city in California is an empty mirage of suburbia in the middle of nowhere.

This tomb was fashioned with a sliding window for a grieving mother who struggled with her daughter's death.

The remains of a failed attempt at medieval nerdery are hidden deep in the woods of Virginia.

This secluded walking trail is a hidden gem of a Pittsburgh park.

A beautiful oddities shop crammed with strange and morbid curiosities.

A futuristic climate change study is nestled deep within this public land.

The snowbirds here are circus sideshow performers.

One of the steepest streets in the United States makes an intriguing challenge for cyclists.

The oldest surviving presidential residence in the United States.

A 550-square-meter micro-nation off the coast of Britain.

This museum is a full-size replica of an original church constructed during the 13th-century.