Ziggurat in the Sand

My friend Tim and his son Gabe are here for the weekend, and as usual, we went to the beach to construct something out of sand, among other things like swimming. Tim always arrives with interesting ideas, and this year it was for a large pyramid with a spiral path to the top. We began by making the sand pile.

Here's the finished pile, packed down and sprinkled with water to keep it solid and moist. Now, I would have simply cut the spiral path out of this, but Tim had other ideas.

Using...