Lake Galena, Peace Valley Park, Doylestown, PA
I start on the west side of the lake at the two-tiered parking lot.  It's 6.1 miles of fun if you go out onto the road, 6.05 miles if you stay on the path. The path is paved and well taken care of.  There's a dam to run over and you'll find many folks using this path for running, walking, biking, and strolling.  From April 1st to November 1st there are real working bathrooms at most parking areas. YAY! During the winter season there are port-o-potties at each parking area and a working bathroom at the Nature Center at the base of the lake.  The day after the holiday party in 2005, Ali and I went for a run and saw a bald eagle.  You will encounter much wildlife and a scenic run.  It's not flat, but not so hilly either. It's a perfect balance for that mid-range run.
 
I think this would be a perfect spot to have a fun run. There are picnic tables and such at most parking areas where we could enjoy each other's company after a relaxing run.

link to park website