This simple stone memorial remembers a secret, Geneva Convention-defying interrogation base from WWII.

Once forgotten and built over, this historic Black cemetery now houses a poignant memorial.

This brick-lined pedestrian walkway was once a railway tunnel used during the Civil War.

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

Every drop of D.C. tap water flows through this old waterworks.

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

A much-maligned monument to teetotalism.

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

An imposing pair of sphinxes stand guard outside this Egyptian Revival tomb.

A bronze statue of Mister Rogers in the neighborhood where he grew up.

This quarter-mile tunnel under the Bluff in Pittsburgh bends at a 45-degree angle.

An ode to filmmaker George A. Romero, who used the mall to film an iconic horror movie.

The Pennsylvania shopping center was once the setting for the 1978 film, "Dawn of the Dead."

Once the most painted on object in the world, this short campus fence is well on its way to being so again.

Meet your friends, marry your true love, or tell your enemies to kiss your butt under this historic Pittsburgh timepiece.

South Philadelphia is home to Keith Haring's only surviving in situ collaborative public mural.

Long hidden under grime, the politically radical murals of a little known Yugoslavian master are finally getting their due.

This elaborate towering structure was once famed for its revolutionary height.

An 18th-century Catholic church converted into an eccentric temple of music and bacchanalia.

The internal railway of one of the biggest steel plants in America has been transformed into a linear park with unique industrial views.

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

This church in Pittsburgh is home to the largest collection of religious relics in North America.

This little museum in the town where zombies were born celebrates the living dead.