I believe railroads are an underutilized feature in the game at the moment, and think they could be improved by adding a new district based on them. (I also believe infrastructure is an underrepresented component in Civilization in general...but that's a topic for another thread.) The Railyard should provide major adjacencies to harbor and industrial zones, but I think the key feature would be that constructing railroads is no longer something military engineers do. When a Railyard is constructed, it would automatically create a railroad between the railyard and the city which created it. Then, I think it should also connect to any other railyards and/or cities within X tiles. (maybe it also connects to the industrial zone and/or harbor) In addition, the railyard could house buildings for things like a monorail, or subway system, though I don't know what bonuses those would give exactly. There's probably a number of other cool features this could include, so chime in with your thoughts! Also, if you have an idea how to go about making a new district mod...I would appreciate a brief tutorial! I have the modbuddy system and a basic working knowledge of what to do...just need some insight into what requires changing/adding.