Join Park Staff at the Hell's Hollow Parking lot to embark on a 7.2 mile guided hike of the Slippery Rock Gorge Trail on National Trails Day.  The Slippery Rock Creek Gorge is a National Natural Landmark, created by the draining of glacial lakes thousands of years ago.  Huge boulders litter the valley floor and several breathtaking waterfalls add a natural beauty to the landscape.  This hike is considered a more difficult hike, so hikers should be in good physical shape and be prepared to traverse steep, rocky and uneven terrain.  Pre-registration is required.  To register call the Park Office at 724-368-8811.  Program will be limited to 12 participants.  Lunch will be provided.