Concrete "steps" of a spiral dropshaft, in the West Kittsondale storm drain, Saint Paul, Minnesota. The spiral staircase arrangement is one of several possible methods of producing a great change in sewer elevation while minimizing erosion and, indeed, the real estate "footprint" of the drain. One of three similar spiral dropshafts in this drain, this is the key attraction that draws adventurers - and photographers - to explore it's several-mile length.