Franklin Park, at 500-plus acres and part of the Emerald Necklace, is an underutilized resource – partly because it borders a sketchy neighborhood, and partly because it is so huge. Still, on weekend afternoons the park is full of families from the nearby neighborhoods of Jamaica Plain, Dorchester and Roxbury. The Franklin Park Zoo is contained within the park. Take the orange line to Stony Brook, Green St or Forest Hills and head east until you reach the park’s western edge.