While the tunnels look the same at the start, they soon branch off to different locations. The amount of crusted goo in the passage reduces down to only occasional clumps, and after about a hundred yards they can find that there are lights on the floor, much like in an airplane aisle or like in the pod caverns. Given Stacy's size it's about another quarter-mile to the end of the tunnel, from which emanates the sound of churning, and given the upward slope of the passage it might take them ten minutes or so to reach the room at the end.