Various condottieri later ruled in the city, such as the Visconti; several landmark fortresses remain from this period. In 1434, 1438, and 1470, Imola was conferred on the Sforza, who had become dukes of Milan (Lombardy). It was again brought under papal authority when it was bestowed as dowry on Caterina Sforza, the bride of Girolamo Riario, nephew of Pope Sixtus IV. Riario was invested with the Principality of Forlì and Imola. This proved advantageous to Imola, which was embellished with beautiful palaces and works of art (e.g. in the cathedral, the tomb of Girolamo, murdered in 1488 by conspirators of Forli). The rule of the Riarii, however, was brief, as Pope Alexander VI deprived the son of Girolamo, Ottaviano, of power, and on 25 November 1499, the city surrendered to Cesare Borgia. After his death, two factions, that of Galeazzo Riario and that of the Church, competed for control of the city. The ecclesiastical party was victorious, and in 1504 Imola submitted to Pope Julius II. The last trace of these contests was a bitter enmity between the Vaini and Sassatelli families.
