So here I am again,

As I don't have any special project in mind right now, and if I have i don't want to work on them, I had the incredible ideia of drawing an Underground City, like the legendary dwarves cities on RPG games

The problem is, I don't have ideia how to start it, so I "googled" it, but couldn't find anything helpfull, thats why i came here to ask if anyone here has a image of a good underground city (with levels, buildings, and other stuff). Hope you can help me