Geometry and architecture: the shape and curves in the nineteenth century drawings of the “Regio Teatro” in Cagliari

Starting from Vitruvian models, theatres changes their geometries through centuries. Between sixteenth and seventeenth centuries, they lost their classicist unity for a model organized into two distinct parts: the perspective space of the stage and the auditorium. The early modern building introduced an elongated auditorium drawn with U shape. The following geometrical evolutions were closely conceive to guarantee perfect views from the stands to the stage. In a second time, the U-shaped plan is declined into mixtilinear profiles, reaching finally to elliptical or ovals shapes or to horse-shoe shaped theatres. The Teatro Regio is located in the Castello of Cagliari, along the medieval city walls. The history of this theater began in 1767 with the project commissioned by the Baron Francesco Zapata to the piedmontese engineer Saverio Belgrano. The archives keep some drawings illustrating an U-shaped solution for this plan. In 1831, the early building was redesigned by Giuseppe Cominotti on a horseshoe shape. A third and final project is directed by Gaetano Cima in 1836 when the architect is committed to complete his work. The Teatro Regio was badly damaged by the bombings of Cagliari in 1943, during World War II.