Rail trail to the ghost town of Rausch Gap. Typical rail trail that can get boring out and back but worth the trip to see the ghost town.
Take US-322 West out of Harrisburg and exit onto PA-225. Turn left onto Erie Street then right on Susquehanna Ave. Go about 4 and half miles and get onto Stony Creek Valley Road to the trailhead.
http://www.singletracks.com/item.php?c=1&i=1240