Ringing Rocks County Park in Eastern Pennsylvania was a huge hit with the kiddos (and I really had fun there, also!). Ringing rocks is basically a big boulder field. You bring your own hammer, and you bang on the rocks. There is some trial and error to it - not every rock rings, and sometimes you have to hit several different areas of the really big boulders to find a good spot. But when they ring, it's SO COOL! My kids really enjoyed scrambling and climbing around on the boulders, aside from the hammering and ringing. There are also really nice hiking trails that loop out from the boulder field. We found some really interesting geological features, including what looked like a dried-up waterfall (or a spot where there had once been a waterfall, but maybe the stream pattern shifted?).