I've been thinking this system where trade routes would be 'physical' things that goes through map tiles: Trade route goes from city to city It takes (usually) the shortest path Tiles have 'movement' cost for trade routes, for example river: 0.1, coast 0.2,road 0.5 flat land 1.0 etc. Tile that has trade route gets +1 commerce yield. Cumulative if more trade routes go though tile. Possibly max trade route commerce bonus limit. It would be good idea to build city where trade routes are likely to cross. Trade route can go from home city to visible city on map with open borders. You want to always search for better trade routes. Trade route doesn't go though unrevealed tile or through hostile territory. Enemy unit on trade route can steal some of revenues each turn. For the performance reasons, maybe the number of trade routes would be limited per nation, adjusted by tech, civics etc. The reason I'd like this system is that it would give more strategic value to locations like straits, major rivers, mountain passes, and so on. Something that civ games seem to be lacking. Any comments?