I wiled away on this over a couple of boring afternoons. I work on the computer so much I just wanted to get some time with a good ole' pencil. The idea is there's a chasm or sinkhole with great spikes of rock that point into the center and a tower has been built up from the bottom that intersects with the ends and middle of the spikes. Part of the structure is natural, most man-made rock work and some wooden fixtures.
I apologize for the lower quality of the image I only have a little digital camera to get it into the computer with at the moment but if you want to see a larger version hit Download.
Drawing took up most of a 14x17 tablet page.