A quick area for a beginner or a short jaunt, a walking path to deactivated railroad. Past Sewall's Falls' Bridge is slightly more technical (mostly flat with roots and small rocks) a good place to start to learn trail riding. Along the river the whole way.
Exit 15W on 93, down North State St., right at Beaver Meadow Golf Course, left after Rail crossing. Either park at Monoro Trails before train tracks, or Sewalls Falls parking areas, Monoro Trails is 1 mile one way double track along pond, Sewalls Falls is 1.75-2 miles one way alond the man made canal under the bridge, you can continue across rails for about .5 mile or ride down rails (still tied) to loop back to parking area.
http://www.singletracks.com/item.php?c=1&i=8360