Sigismondo entrusted the execution of his plans to Leo Battista Alberti, who had to encase in a shell of classic architecture a 13th-century Franciscan church.
Alberti solved the problem with marvellous skill, blending the old architecture with the new style of the Renaissance, and giving it variety without destroying its unity of effect.
Such was the zeal with which Alberti pursued his task that the exterior of the little Rimini church is one of the finest and purest achievements of the Renaissance, and surpasses in beauty and elegance all the rest of his works.
Alberti came to Rimini, made his design, saw the work begun and then left it to be carried out by very skilful artists, on whom he impressed the necessity of faithfully preserving its general character so as " not to spoil that music."
Much more important architecturally is the church of St Andrea, built towards the close of the 15th century, after plans by Leon Battista Alberti, and consisting of a single, barrel-vaulted nave 350 ft.