Hope you don't mind mud.
I walk the North Trail daily to get to work and back. Well when it is frozen or dry. The trail winds along the Allegheny River from Sharpsburg to the Carnegie Science Center. A third of which is paved and very nice. However the two-thirds that are not paved are riddled with huge mud puddles and quite sloppy. Many runners prefer the packed dirt, but with no trail maintenance the trail has turned into one big sloppy mess over the years. That being said if the weather has been dry and you need to stretch your legs I do recommend walking, running, or biking this scenic trail.