The largest clock face in the United States is twice the size of Big Ben and infinitely more ad-sponsored.

This permanent exhibition celebrates the finest of our heartless automatons both real and fictional.

Solar observatory doubles as a daring display of Expressionist architecture, much to Einstein's chagrin.

Hundreds of protractors affixed to surfaces all over the city.

This spot memorializes one of the greatest plays in NFL history, unless you happen to be a Raiders fan.

The only way to see Pittsburgh is from the top of this lookout point, just like the ancient members of the native peoples did.

The 320-year-old tree that greeted General Lafayette and rerouted an interstate highway.

A painfully obvious spy house sits right across the street from the Russian Embassy.

One day a year it is legal to jump off of this astoundingly tall bridge that spans an Appalachian gorge.

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

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

Found art has transformed this Pittsburgh neighborhood into a psychedelic dream.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

One of the steepest streets in the United States makes an intriguing challenge for cyclists.

Before Nixon, "watergate" meant canals.

The whole world in one water tank.

The U.S. Fish Commission’s effort to mass produce carp.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

Steepest flood safety railway in the entire world.

A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

The last of Philadelphia's wood-paved streets is now a landmark of terrible engineering.

The fastest transatlantic ocean liner sat abandoned in a Philadelphia shipyard for decades.