Since they closed the steel mills, The Holiday Bar, Forbes Field, and the Iron City Brewery, I'm not sure why anyone would need to go to Pittsburgh
If someone insists: after lunch at Primanti's on 18th Street, drive through 28th and Liberty Avenue where George Westinghouse invented the airbrake in his shop and the Railroad Strike of 1877 started.
Go to 3339 Penn Avenue to see the Roberto Clemente Museum- better known as the quarters of 25 Engine and Truck. Ask to see if the highwater mark from the Flood of 1936 is still in the basement. Even better, see the Captain's office behind the sitting/watchroom/kitchen. Over 50 years ago that's where Entropychaser slept buffing the night tour. The Captain slept upstairs where there was an air conditioner.