This titanic steel chain linking two buildings was installed without permission but instantly beloved.

Hell on Earth is actually a small town in Michigan where anyone can be mayor for a day.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

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

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

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

This 29-ton granite ball spins around at the slightest touch thanks to a scientific phenomenon.

This museum devoted to the gothic author holds such interesting ephemera as his socks and walking stick.

The U.S. Navy’s preposterously detailed mini battleship took 77,000 hours to complete.

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

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

A museum dedicated to the history and exploration of both popular music and science fiction.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

Now famous as the "Harry Potter bridge," this impressive concrete viaduct has long been an icon in its own right.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

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

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.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

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

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

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

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

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