If you're not averse to the most fast-casual of fast-casual dining, pretty much everyone in Pittsburgh treats Primanti's ike a real institution.

I'm biased because I live real close to it, but if you're not too squeamish Center for Postnatural History is a treat. Further afield the curio shops in Allentown neighborhood are a real trip. There's also Randyland, Photo Antiquities, and your more fancy museums/cultural sites like the Warhol, Heinz, Carnegie Museum of Natural History etc.