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

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

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

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

This unique museum cafeteria showcases the history and regional diversity of African American cuisine.

One of the three perfect vellum copies of this historic book known to exist is on display in a specially-designed case.

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

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 tunnel under the Capitol Building where Congress takes out its trash.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

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

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

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.