Ever wonder what's below the surface of western Pennsylvania? Come for a hike into Laurel Caverns, investigate the fabled Fourth River, visit the Bug Rooms at the Carnegie Museum of Natural History, and zip through several tunnels around here. We ride the T, look under the Dormont Pool, and descend into several basements (including two at Marshall Elevator!) We consider a Pittsburgh potty and follow the sewer to ALCOSAN. You can watch the harvest at Creekside Mushrooms, see some of what's stored...