A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

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

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

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

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

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

The only Leonardo Da Vinci painting in the Western Hemisphere.

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

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

This large garden vase urn has nothing to do with the seventh U.S. President—it was designed by one landscape designer to honor another landscape designer's contributions to the National Mall.

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

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

Ruins from the Parthenon and petrified wood line the interior of one of the world's most famous monuments.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

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

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

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

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

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

D.C. once had its own tiny rival to the New York Stock Exchange.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

The word "Watergate" will forever be associated with the infamous scandal in 1972, but this fountain is famous in its own right.

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