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

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

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

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 privately owned cemetery that holds room for Washington's finest when they step down from life.

Light bulbs, scrap wood, and tinfoil comprise this homemade throne of the gods.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

The "lovely red Vega" of the legendary record-settling pilot.

The national park was once a plantation estate.

The oldest continuously operating fish market in the United States.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

The famous abolitionist’s preserved estate is one of Washington's finest monuments to its great Black citizens.

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

It was once the base for a series of domestic terror attacks.

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

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

The house where John Wilkes Booth conspired with his co-conspirators.

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

Largest Roman Catholic church in North America.

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

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

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

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