The Floor Plan of Sant'Ivo by Borromini

Borromini‘s use of symmetry is extensive, also in three dimensions, in architectural structures, plan and details. Scholars, at times point to symbolical meanings weaved into his compositions. We examine the plan of the floor of Sant’Ivo alla Sapienza, in Rome Italy, and analyze its symmetry group. This symmetry group is that of an equilateral triangle, and is also clearly perceivable as such on the lift of the walls. This merely mathematical analysis agrees with historical documents on the use of the compass by Borromini, and disagrees with a spread interpretation of symbolical order, which would require a hexagonal symmetry. This analysis, in turn, yields a further question on the organization of curved surfaces typical of Borromini.