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

Go take a picture with the inventor of the daguerreotype photographic process.

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

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

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

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

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

Coins and medals straight from the mint await visitors to this shop in the nation's capital.

A much-maligned monument to teetotalism.

A spectacular tribute to statesman and philanthropist Andrew Mellon.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

The National Park Service’s best-kept secret with views that rival any in D.C.

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

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.

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.

This groundbreaking 16th-century map is known as "America's birth certificate."

This lovely pocket park is one of the most under appreciated in D.C.

This lonely waterfront memorial to the men of the Titanic was erected by the "Women of America."

Now a living classroom, this house was once the home of Reverend James Clinton Dent, a formerly enslaved man and a pastor.

A super-sized promotional trick that is now a D.C. landmark.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

A striking memorial to the 21 lives lost in an explosion at the Washington Arsenal

The remains of a historic plantation nestled in between a parking lot and the rental car return at Reagan National Airport.

The romance of early commercial flight still fills this Art Deco destination.