Great feedback friend! I love to hear these kinds of questions. My original thought when I began drawing this, was to essentially create a city and what the system might look like underground. I know I could have put a lot more detail and focus as of what really is hidden underground. However I just kept drawing and kind of focused in on the city details rather than anything below that. I would actually like to redo this sketch again, but with more intricate details given below the surface. Maybe with the pipes leading to something even bigger. A creature perhaps? Could be anything. As for now, I agree 100% on your constructive criticism. Thanks again friend.