Here are the vitals if you'd like to build one of these yourself:
Spokes: 16 spokes sections at 50.5" each
Treads: 8 treads sections at 39" each
Rim: 16 rim sections at 39"
I used 3/4 inch PVC and glued the pieces together with PVC joint cement. You'll need a whole bunch of connectors (T's & quads).
Point of View.
From above #1.
From above #2.
Aboard the submarine.
Me and my tail.