I refer to my Distict Line and associated session for ideas. I have seen some attempts at tunnel track for the LU but they are not really successful and once you have seen one station you have seen them all. As the district line is subsurface for only a part of its journey, tunnel construction is easily made with the parts with only one side wall, to allow for complex junctions. My trackline shows the whole of the circle line except for the Hammersmith branch, and the District lline from Upminster to Just west of West Kensington. I have yet to upload my extension to Putney, but I haven't finished it. The track line is nearly geo accurate, and some stations have accurately real named junctions and signals. Feel free to mess about with it. Apart from the track there is no scenery, as who need scenery underground? The overground sections also have no scenery but as the constrcutons was in proto form I had no interest.
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You may need to download some AJS material. and use andi06's rules.