The beloved, war-tested mascot of a Union regiment graces their battlefield monument.

This historic building is now home to the Public Access Corporation for the District of Columbia.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

The tunnel under the Capitol Building where Congress takes out its trash.

A portal into the bricked up canal that runs through the heart of Washington D.C.

Where the U.S. government kept its actual treasure, before Fort Knox.

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.

Largest Roman Catholic church in North America.

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

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

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

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

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

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

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

A painfully obvious spy house sits right across the street from the Russian Embassy.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

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

This grand gothic brewery has been pumping out suds for over a hundred years.

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

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

In this case, 'zero' marks the spot where the iconic Old Spanish Trail ends.

The only working large-scale tea plantation in the United States.