My wife and I rode a few roads in Rockport yesterday before the rain and today she dropped me off in Watertown so she could attend a social event and I could escape by biking back to Sherborn.
http://www.mass.gov/dcr/parks/charle...perCharles.htm
I hopped on the trail along the Charles River in Watertown Square. DCR has a Great Blue Heron logo on their markers
and I saw several (socially) plying the Charles River in Watertown and Waltham.
DCR uses blue painted heron footprints to connect trail sections but I still got slightly lost trying near the western end. It was well used, very pleasant and well maintained. There are root bumps but they are well marked and several section are stone dust so larger size tires are a little easier. A 1.5 min promo video