This stately mansion, built in 1787 by America's first Secretary of the Navy, is rumored to be one of the most haunted buildings in Washington, DC.

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

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

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

Largest Roman Catholic church in North America.

Home to a vast and influential collection of Shakespeareana.

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

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

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

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

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

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

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

A nostalgic bibliographic gem.

The national park was once a plantation estate.

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

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

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

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

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

People escaping slavery may have hidden inside a corpse vault.

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

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