Once America's tallest structure, now a Baltimore landmark.

It’s not hard to see why the historic Peabody Conservatory of Music’s library has been described as a “cathedral of books.”

This simple convenience store sits on the location where the Ouija board was named—and has a plaque to prove it.

The design of this historic domed church was influenced by Thomas Jefferson and intended as a statement of religious freedom.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

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

The bridge's highly-contested plaque (once again) honors Confederate President Jefferson Davis.

A wondrous old library overlooking the nation's capital.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

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

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

The most decorated dog of World War I is preserved in the Smithsonian.

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

The most accurate timepiece in the world.

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

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

A double agent hid information for the Soviet Union beneath this bridge for more than 20 years.

Huge masonic hall in Philadelphia with lavishly themed rooms.

One of the oldest of its kind.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

Golden and naked, the figure that was once the highest point in New York is all that remains of the second Madison Square Garden.

Yo, Adrian!

The world’s first penitentiary, meant to be humane, drove men insane.