The third level begins in the center of the map, and drifts in a clockwise spiral until ending at the lake in the upper right corner. There is no connection with this level and the three shafts on the right except back up to the first level and down the shafts; some of what's written on this level should give the reason. Describing it, the players should get the sense that A) some kind of accident occurred; B) the piled furniture in front of the two doors was an attempt to close off the interior; and C) things have been left deliberately behind for reasons that are unclear. It might also occur to players that what was left behind is somewhat more active than might have been expected ... since the 'closing off' effort is fairly weak considering. Ah, but this is human nature.
As before, this can be read more clearly on the wiki, here.
These are kind of fun. I'd like to point out that none of the odd or unusual things described above are rehashes from campaigns I've run in the past. To the best of my mind they are completely original, being what I thought of to fit the overall concept as I was designing and describing that particular room. This had a lot of description only because the things I thought of were hard to outline in just a few words.
I'm enjoying how well things are coming together. Of course, there's only a slight chance the party would even come down this way at all ... and I ought to get around to describing the shafts from the beginning. A few of you might have guessed that those shafts lead to a second attempt at whatever the first attempt failed at. You'd be right.