An eerie site of reverence for those who have completed an epic journey.

A curious whirlpool formation supposedly capable of entangling or engulfing branches, tree trunks, or whole rafts full of hapless tourists.

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

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

A wondrous old library overlooking the nation's capital.

The world's oldest soul food restaurant is also one of its best.

This unique museum cafeteria showcases the history and regional diversity of African American cuisine.

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

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

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

An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

After his presidency, George Washington planned to live only a few blocks from the Capitol building.

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

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

Home to a vast and influential collection of Shakespeareana.

Depending on who you ask, this controversial treehouse is either a charmingly creative child's playhouse or an illegal encroachment on public land.

This groundbreaking 16th-century map is known as "America's birth certificate."

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.

Outside the Department of Transportation, a collection of artifacts honors the history of how we get around.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

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.

This small hut in the middle of a parking lot was once the wooded sanctuary of the 'Hermit of Montrose.'

Florida’s half-sized replica of the Vietnam Veterans Wall.