The design of this historic domed church was influenced by Thomas Jefferson and intended as a statement of religious freedom.

The remnants of a wooden-hulled fleet built and abandoned in WWI, now home to a thriving ecosystem.

The land is home to swimming ponies and a legendary 18th-century treasure.

The trials and tribulations of marking Poe's grave.

It's not hard to see why the historic Peabody Conservatory of Music's library has been described as a "cathedral of books."

This taxidermy horse was a Civil War hero.

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

Before founding the American Red Cross, Clara Barton had a tremendous humanitarian impact by locating thousands of missing soldiers.

When it comes to handsignals (and colonialism) rock always beats scissors.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

The towering figures were created from the cemetery's fallen old-growth trees.

The "lovely red Vega" of the legendary record-settling pilot.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

This restaurant has been a haven for D.C.'s LGBTQ community since the 1950s.

Largest Roman Catholic church in North America.

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

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

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

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

The United States Capitol's former columns still stand.

A spectacular tribute to statesman and philanthropist Andrew Mellon.

The story behind this beloved toy—named for Theodore Roosevelt and owned by his grandson—is more complicated than you might guess.