I see 20 identical square boxes, stacked. IMHO, each side of each box is also identical to each other side, but the facing edge is curved, and the boxes are rotated so the corners match.
Lay one with its back flat on the ground, I think you'd see high corners on diagonal sides and low corners on the other diagonal.
Any curve (to other than the edge) that y'all are seeing is an optical illusion.
That's my story and I'm sticking with it.