The Delaware and Raritan Canal runs for miles through Lambertville.  Perfect for a run, biking, or even just a nice stroll along the canal.  You'll likely see ducks and geese, and a couple of local cats.  If you're lucky, you may spot the beaver.  South of town about half a mile you can find the wing dam jutting out into the Delaware River, where you can sunbathe or dangle your feet in the river.  North of town, you can walk on either side of the canal, and on the path between the canal and the river, you'll run into an old rail car, nicely decorated by graffiti artists.  The canal can provide for a shaded promenade, fall foliage, or even raspberry picking depending on the time of the year.