The tower looks to be made of the parachute fabric mentioned earlier. I've purchased it at Joann's for use as an outdoor banner. It is not difficult to sew (only problem I had was with appliquing the Old English style letters for the name). The idea of hula hoops to create the circle shape also sounds like a very simple and cost effective solution. To do the cone shaped top you can just cut a circle then cut a pie shaped piece out and overlap those edges and stitch. I also like the idea of suspending the tower from the ceiling. You can get one of those hooks like for hanging plants or lamps and attach a hanging loop at the top of the cone to the hook.
I think you can do this fairly easily actually!
Do let us see it when you're done.