THE TUNNELOne of the neat things about model railroading is the tunnels. Real railroads will go miles out of the most direct route to avoid the expense of digging a tunnel, but because modelers want the loops in their limited area to be obscure, they make frequent use of them and it's always a kick to see a train come bursting out of one. The rocks and drainage paths suggest a barrier where tunneling was the only solution.