There is a 15 paved loop that runs next to the Charles river from downtown out to Watertown. For mos of the way there is a dirt path running along side it. Great early season training rides or for a quick spin when you can't get out to the trails. Flat as a fritter so you will need your big ring. I usually head west from Back Bay on the south side of the river. Look out for other bikes, joggers, and pedestrians. It is best to avoid it during busy times so either ride early in the AM or any time after dark.
From Boston: Take Storrow Drive West. Pass the Harvard Square exit and then get in the left lane. Bear left at the Rte. 2 interchange onto Soldier's Field Road, following the signs for Newton (do not cross the Eliot Bridge to Cambridge).<br /><br />For the bike trail: Access to path is plentiful throughout the city just head to the river. If you are driving in head to Back Bay if you can find a meter spot great. If not park at Boston Commons or one of the other garages. If you start in Back Bay there are several foot bridge to get you across Storrow Dr. just head north on Arlington, Dartmouth, Fairfield or Mass Ave till you hit the end and you will see on of the bridges.
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