Rainy days make me think of the Paw Paw Tunnel. When I'm in Allegany County on a rainy day, I go out of my way to enjoy the tunnel's spectacular man-made natural wonder. It holds one of the best secrets of the canal.

As I approach the upstream end I listen for the familiar roar. When I hear it my pace quickens. The fascinating features of the tunnel that usually captivate me - the rope burns in the railing from untold thousands of canal boat tow ropes, the speleothems that grace the sides and ceiling of the tunnel, the hole in the wall that exposes the many layers of brick - all are distractions.

My reward cascades over the downstream portal of the tunnel, a waterfall that flows only when it rains. When the canal builders created the tunnel, they also carved a long approach out of the mountain on the downstream end. In creating this half-mile long man-made canyon, they changed the drainage patterns of the mountain, focusing much of it down over the North portal into what is now known as Tunnel Hollow.

I rarely get to share this beautiful experience, because most people don't visit the tunnel in the rain. But the secret's out now. Maybe I'll see you at the tunnel next time it rains.