Looking good. The drop shadows are a little off though. I assume the highest point is the outer edge of the stands, therefore this should cast the strongest drop shadow. As it is, your heaviest shadow is being cast from the wall between the lowest seats and the arena floor.
Equally with the towers, if you can have them cast a large drop shadow outside the edge of the stands and a small one inside the stands then it will help guide the viewer to understand your different heights.