​What is this roughly ~20 foot chain hanging from a steel beam with rocks at the bottom at a train station/bus stop?

I don’t know if this is an art installation but I wasn’t able to find anything on the Wikipedia page or a quick Google search for this train station. It’s roughly 20-30 tall a chain hanging from an iron beam that comes down into a bed of rocks in a garden near the waiting room of an Amtrak Septa train station.