Symmetry in Architecture

What does the seventeenth-century Rundetarn (Round Tower) of Copenhagen have in common with the thirteenth-century Leaning Tower of Pisa? Or Houston's Astrodome, the first indoor baseball stadium built in the United States, with the vast dome of the Pantheon in Rome? Or a Chinese pagoda (fig. 1) with the Sydney Opera house (fig. 2)? A first response might be "shape" but a more accurate answer would be "symmetry". Each of these strange couples of buildings share a different kind of symmetry that links them, in spite of their temporal and cultural differences. As Magdolna and István Hargittai have noted, symmetry, in architecture as in other arts, is "a unifying concept".[1]