If you do mean the Gray's FERRY Tunnel go to the Yahoo map of Philadelphia. It is near the intersection of Grays Ferry Ave. and 34th St. in the city's southwest quadrant.There is a bridge going over the line just to the south of the tunnel. Best time for the sun is late morning through mid afternoon. If you get there earlier you can photograph trains going into or out of the old B&O's Eastside yard just by facing away fron the tunnel. There is an exit from the Schuylkill Expressway, I -76 nearby but I don't know the name or number of that exit. Also just a few blocks away there is the bridge over the Schuylkill near RG Tower (still staffed). You can photograph trains coming off the bridge without going onto CSX property. it's agood spot.