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.

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

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

A line of blue paint marks the route of the inaugural parade.

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

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

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

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

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

A diminutive memorial marks the site of a successful assassination by a right-wing death squad in America's capital.

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

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

There’s a special club house at the top for the bell ringers.

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

There’s a hidden military meme engraved on the World War II Memorial.

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

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

A computer bug so primitive it was an actual insect.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

A nostalgic bibliographic gem.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

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