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

A haunting tribute to pioneering photographer Clover Adams.

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

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

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

There's a crumbling old mansion inside the Smithsonian National Zoo.

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.

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

The oldest continuously operating fish market in the United States.

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

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

When it opened during the final years of the embargo, all the drinks and cigars were free.

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

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

A Spiritualist house of worship where believers communicate with the dead in the spirit world.

The national park was once a plantation estate.

An Industrial Revolution-era public work that purified water using nothing but sand.

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

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

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

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

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

People escaping slavery may have hidden inside a corpse vault.