Riverside Greenway, Lewiston
This is a great paved path that runs along the Androscoggin River and past a cemetery. You can see a good map here, with suggestions on linking this trail to other nearby trails. You can also walk along an unpaved and un-blazed trail in the neighboring Sunnyside Park, which continues a little ways along the river.
Directions: You can pick up one end of the path from Tall Pines Drive, where the road makes a sharp curve. I think it’s okay to park alongside the quiet street here, as long as you heed the parking signs. Or you can park at trailhead near Sunnyside Park, at the intersection of Winter and Whipple Street.