While I loved the original rook tower design, I found the helix challenging for my poor Printrbot Simple Metal, and redesigned the model with a central column. I like the cleaner interior design. I also modified the base to remove the need for printed supports. All overhangs are now supported by 45 degree angled slopes.
Update: Printed the file in black PLA with no supports needed. Worked great. Minimal interior stringing and no more sagging roof/floor. If anyone prints it in transparent material, I'd love to see the result! [Photo added - Sept 23, 2015]
Should print with no supports needed.