This unique historical monument features large concrete spheres designed to resemble fallen stars.

Atop this media building, two hives containing more than 30,000 bees keep the surrounding area vibrant.

The entrance to this sinisterly named tunnel hides behind a Tim Hortons.

An unoccupied lighthouse encased in layers of ice from the waters of Lake Erie.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

The U.S. Navy’s preposterously detailed mini battleship took 77,000 hours to complete.

There’s a hidden military meme engraved on the World War II Memorial.

The walls of the iconic dome are hollow and have a secret stairway.

People escaping slavery may have hidden inside a corpse vault.

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

A public art jibe at one of the United States’ oldest and longest-serving senators.

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

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

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.

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

A derelict bit of transportation infrastructure hidden in the woods.

A wondrous old library overlooking the nation's capital.

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

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

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.