Propping Tower Grove Park is always a noble endeavor, and there's no better way to experience its beauty -- especially now, in the fall, when the trees are exploding and the squirrels are starting to panic. But we're looking for a ride, and a cruise through the Grove is more of a jaunt. The best in the city is also the biggest and most obvious: the St. Louis Riverfront Trail, which stretches nine miles from the north side of downtown at the old Laclede Gas building to about a mile and a half south of the old Chain of Rocks Bridge. From the trail, you simultaneously experience both St. Louis industry -- ride past Mallinckrodt! -- and its natural beauty: the banks of the Mississippi; a touch of beautiful prairie; abandoned factories and depots; Baden, glorious Baden; and, ultimately, the old Chain of Rocks, upon which bicyclists can park, peer down on the river and, if they like, spit into it.