Rudder Controls This giant gear’s sole purpose was to turn the ship’s single rudder in all conditions. Similar Images ...based on the tags: gears, pipes... A typical large mine tunnel. You can just make out the narrow gauge rail. This might have been part of the Pioneer Pellet Plant. It looks to be a ball mill, which pulverizes ore by spinning it with thousands of ball bearings. The ‘working’ part of the furnaces are about a story above ground level, so the catwalks snake above the tree line. If there were no other options, operators could climb this ladder from the Communications Room to the surface, after opening two heavy steel hatches, of course. The only good shot I have of the top of Battery A, in the upper left. Though it seemed to have been disused before its neighbor it had a lot less growth on it. The generator hall of the last power station, as seen from the gantryway. Filters and fans to draw air into the boilers in the second power plant. Workers would undoubtedly prefer to use the belt manlift on the right. The newer tunnels were fitted with these fluorescent lights, although some skylights (block glass embedded in skywalks) let in some natural light during the day.