Look closely and you’ll notice that the color changes a third of the way up the tower.

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

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

Washington's iconic carousel has a nice piece of Civil Rights history.

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.

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

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

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

The Kirkland Monument remembers a selfless Civil War hero who braved the battlefield to give water to his dying enemies.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

Located at the former Lorton Prison the Lucy Burns Museum tells the story of the 91 year history of the prison including the dark chapter of its involvement in the women's suffrage movement.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

An overgrown garden stands as a grim marker of an unrealized dream.

This war hero's old shop remembers the fine line between medicine and quackery during the Revolutionary War.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

At 207 feet, one of the world's longest continuous escalators.

Yo, Adrian!

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

An almost life-sized elephant named Ms. Ellie greets visitors at this jumbo-themed museum.

Outsider art meets paleontology at this roadside reptile repository.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

This pre-Revolutionary War grist mill ground corn and flour for soldiers in seven American wars.