sentences:  While one of the plans (scheme C) had a hexagonal shape and level floors for the galleries, all the others had circular schemes and used a ramp continuing around the building.He had experimented with the ramp design in 1948 at the V. C. Morris Gift Shop in San Francisco and on the house he completed for his son in 1952, the David and Gladys Wright House in Arizona.Wright's original concept was called an inverted "ziggurat", because it resembled the steep steps on the ziggurats built in ancient Mesopotamia.