We've been on almost all of the bike trails in Pittsburgh, and have to admit, the Ghost Town Trail starting in Black Lick, PA (about an hour east of Pittsburgh) may be our favorite we've been to so far.
This trail covers 46 miles (~10 miles of which are on an extension trail) from Black Lick to Ebensburg. During our first visit, we hit up the first 25 miles of this route (turning around on the main trail in Nanty Glo) and saw so many beautiful sights.
As an added bonus, this trail was quite an easy ride!