Barcelona would be a great city! It has an extended metro with 11 lines.
I don’t know if you guys are still taking suggestions for future updates, but… MANILA, PH!
Here’s a map of the planned lines in the Greater Metro Manila area
Note: the teal line is actually a rarely-used ferry-line the mapmaker integrated into the map.
And here’s a map of the current rail transit lines and the rivers in the area (more geographically accurate)