The spiral design recalled a nautilus shell, with continuous spaces flowing freely one into another. Wright ascribed a symbolic meaning to the building's shapes. He explained, these geometric forms suggest certain human ideas, moods, sentiments – as for instance: the circle, infinity; the triangle, structural unity; the spiral, organic progress; the square, integrity. Forms echo one another throughout: oval-shaped columns, for example, reiterate the geometry of the fountain. Circularity is the leitmotif, from the rotunda to the inlaid design of the terrazzo floors.