Being originally from Philadelphia, I remember that that every time it would snow I would head out towards Valley Forge to do some 'winter cabin' shots. Snow covered cannons were great too. There's an old covered bridge at the NW side of the park, where rt. 23 exits. It's a left turn at the traffic light denoting the end of the actual park, then about a mile down that road (I believe it's 452?) Short walk to get set up with the snow-filling creek flowing under the bridge...