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

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

Known as the "Valley of the Moon," this Jordanian wadi is one of the most amazing desertscapes on Earth.

A stunning mosque owes its design to an Ottoman ruler nicknamed "the Butcher."

Decades before the scandal, this staircase on the river was a literal "water gate."

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

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

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

A derelict bit of transportation infrastructure hidden in the woods.

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

An overlooked memorial honoring the local Washington residents who died in World War I.

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

Perhaps the most scandalous statue of America's first president.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

The most accurate timepiece in the world.

Largest Roman Catholic church in North America.

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.

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

The site of the climactic scene from the classic horror film is now a historic landmark.