Hi Smeagol01, To get the tunnel tracks to link up tight, sometimes you need to modify the entrance/exit areas of the mountain. First lay a track perpendicular to your line where you want to enter. Use the terrain tools or lay a few linked tracks into the hill to get a straight cliff-edge to construct your double track tunnels into and out of the mountain. Kind of the same principle as crossing a river with double wide bridges. > The closer you approach the river to perpendicular, the easier it is to cross with multiple tracks. Sometimes I need to prep both the entrance and exit.