The exterior of this monument (Fig. 35) has much merit in its general form and proportions. The great central square mass, visible from the ground upward, gives the sense of support for the dome which the eye demands, and the apses with their half-domes are effectively grouped in subordination to the crowning feature. But this merit, which Todi shares with many other buildings of the Renaissance, is primarily due to the Byzantine scheme adopted, and cannot, therefore, be wholly credited to the Renaissance architect. [Illustration: FIG. 38.--Interior of San Biagio.] [Illustration: FIG. 39.] A variation of this scheme occurs in the church of San Biagio at Montepulciano by Antonio San Gallo the elder, and begun in the year 1518. Here the arms of the cross (Fig. 37) are square, with an apse added to the eastern arm. The interior is ornamented with a single, and very heavy, Doric order (Fig. 38), framing arched recesses in the imperial Roman manner. The use of pilasters on the angles makes the awkward combination of a pilaster coupled with a column necessary, and since the entablature is in the plane of the wall, it has to be broken into very salient ressauts in order to cover these members. Above the entablature is a low ledge in retreat, broken into ressauts in conformity with those of the entablature, and from these ressauts coffered archivolts are sprung under the ends of the barrel vaults which cover the arms of the cross. The Doric order is designed here, for the most part, in close conformity to ancient models, save for the pilaster on the angle, which does not generally occur in Roman monuments. The common Roman treatment of the angle is shown in the arch of Septimius Severus (Fig. 20, p. 41), where the end column of the order is placed at some distance from the end of the façade, which is left in retreat without any pilaster. But Serlio[74] describes the ruins of an ancient Roman building (Fig. 39) that appears to have been a sort of open arcade or stoa, used as a meeting place for merchants, on the angles of which pilasters are set together with columns, somewhat as they were by Alberti in Santa Maria Novella, by San Gallo here in San Biagio, and by many other architects of the Renaissance. He speaks of the treatment of the angles of this building as follows: “The corner pilasters are larger than the others, and were truly made with excellent judgment, for they strengthen the angle with good effect; and from this architects may learn how to design angles with columns and pilasters bound together, in order that the corner may be brought into line with the column, which gives more solidity to the angle. If the said angle were withdrawn into line with the middle pilasters, the façade, when viewed obliquely, with the round column on the angle, would appear imperfect, and for this ... I strongly commend this form of angle because it may be fully seen from all sides.” [Illustration: FIG. 40.--San Biagio, Montepulciano.]