When you drive to downtown Pittsburgh from the airport or I-79, then you are up for one of the greatest transformations in scenery in the US. You drive through lush green hills, enter the tunnel and now you see three rivers, a fountain, mostly flat terrain and Pittsburgh's beautiful skyline. More information can be found here: https://backpackandsnorkel.com/USA/Pittsburgh/Best-Viewpoints/#Fort-Pitt-Tunnel