Pittsburgh was an industrial powerhouse for the better part of a century and the rivers were the highways of industry. To get people and stuff from the barges on the rivers to the tops of the valley, there were inclines. Basically vertical transports on rails that carried people and stuff from the floor of the river valley to the top. Two of them still exist in Pittsburgh. They are part of the transportation system of the city, a distinct landmark and a must do when in town.
You can park at Station Square for the Duquesne Incline or at the Mount Washington Parking lot for the Mount Washington Incline.
For a couple of dollars a person you get an amazing bird’s eye view of the city and can walk along the promenade above where there are viewing platforms. Some great little cafes and and ice cream shop give yo a place to grab a snack or use the facilities.