Around MIT, the route around the river is pretty popular as the map shows. Except at one point you have to choose between a fork in the road -- do you take a right and run right next to the river and enjoy the water, or do you keep running straight and enjoy the rush of cars on Storrow drive as you run. Im more of a car person, but my girlfriend likes to run by the river. Strava shows me that the Storrow alternative is indeed less popular :(

http://labs.strava.com/heatmap/#17/-71.07863/42.35498/gray/b...