This lovely pocket park is one of the most under appreciated in D.C.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

Obscure Freemasons still live in D.C.’s largest private residence.

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

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

The oldest continuously operating fish market in the United States.

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

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

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

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 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.

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.

A wondrous old library overlooking the nation's capital.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

A historic neighborhood church is reborn as a psychedelic arts collective.

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

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

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

The United States Capitol's former columns still stand.