Blast the rocks and drill tunnels beneath cities. At the beginning you have enough time and no major problems. Once the TNT charges are placed you can start the blasting to create the tunnel entrance. The excavated material will be loaded by a shovel dozer on a dump truck and transported to the storage site. As soon as the entrance is cleaned up the huge tunnel drilling machine will march up. But this monster can only start operation if it is supplied with sufficient building material. This has to be delivered by crane and train. You have to steer all vehicles like the maintenance van, crane, tunnel drilling machine or the fire brigade.