PROTIRO. - A small structure attached to the entrance of a church building, a quadriportico, or a portico is called a p.; in its simplest form it consists of a vault supported by two or more piers or columns.
The earliest examples of p. are found in the Eastern architecture of the first centuries of Christianity. That of the church of Egmiadzin, consisting of a small tower attached to the front of the building, dates from the fifth century. Likewise, the side adjoining the façade of the quadriportico of the ancient Vatican Basilica, in the ideal reconstructions available of that building, must have had a p. In any case, in Italy it already appears in the church of SS. Martiri at Cimitile in the eighth century, and thereafter became widely diffused during the Romanesque period. This occurred not only in the characteristic and very simple examples of the Roman churches of S. Prassede, S. Maria in Cosmedin, S. Clemente, and S. Cosimato, where the p. must truly have served a protective function for those remaining outside the church, or, when the p. had two levels, as the place where the guardian watching over the church entrance was stationed; but also in those of northern Italy where, as at Cremona, Piacenza, Modena, Bergamo, Ferrara, Verona, etc., it acquired the status of a decorative element intended to lend grandeur to the entrance of the building. In this sense, among the finest are that of S. Ciriaco in Ancona, a work of the thirteenth century, and that of the side door of the parish church of S. Quirico d'Orcia, whose corbels supporting the short vault are attributable to the school of Giovanni Pisano. - Vedi tav. IV.