great start Tilt! I like the subtle lighting/shading of the bridges and down-going stairs. I presume that the darker the rooms, the deeper they are (to indicate levels) which is - if am right- a nice find. problem may be the overlap between the levels (currently the rooms are a little bevelled so maybe an inner shadow may give some more depth to the rooms....) anyway i'm curious how this will turn out... small note: the water texture seems a little out-of-place to me (a little shiny) but I guess it depends on further texturing... good luck 'n cheers!