Walked around the lake several times. Nice walk. Walk around in a clockwise direction in the afternoon to avoid sun in your face. Go the other way during sunset for a lovely sunset walk.

You can't get lost on this walk/jog in the town I where I went to high school. Just walk around Lake Quannapowitt. The "busy" aspect comes from the popularity of this route for locals getting their daily exercise. The "Moderate" assumes you join the joggers. Otherwise it's fairly easy. The lake is in predominantly residential surroundings, with a few commercial properties.