Florence was the great center of artistic activity during the fifteenth century. The greatest sculptors and almost all of the most famous painters and architects of the time either were natives of Florence or did their best work there. During the first half of the century sculpture again took the lead. The bronze doors of the baptistery at Florence by Ghiberti, which were completed about 1450, are among the very best products of Renaissance sculpture. Michael Angelo declared them worthy to be the doors of paradise. A comparison of them with the doors of the cathedral of Pisa, which date from the end of the twelfth century, furnishes a striking illustration of the change that had taken place. A contemporary of Ghiberti, Luca della Robbia (1400-1482), is celebrated for his beautiful reliefs in glazed baked clay and in marble, of which many may be seen in Florence. [Illustration: BRONZE DOORS OF THE CATHEDRAL AT PISA (TWELFTH CENTURY)] [Illustration: GHIBERTI'S DOORS AT FLORENCE] [Illustration: Relief by Luca della Robbia] One of the best known painters of the first half of the fifteenth century, Fra[236] Angelico, was a monk. His frescoes on the walls of the monastery of San Marco (and elsewhere) reflect a love of beauty and a cheerful piety, in striking contrast to the fiery zeal of Savonarola,[237] who, later in the century, went forth from this same monastery to denounce the vanities of the art-loving Florentines.[238] [Sidenote: Rome becomes the center of artistic activity.] 126. Florence reached the height of its preëminence as an art center during the reign of Lorenzo the Magnificent, who was an ardent patron of all the arts. With his death (1492), and the subsequent brief but overwhelming influence of Savonarola, this preëminence passed to Rome, which was fast becoming one of the great capitals of Europe. The art-loving popes, Julius II and Leo X,[239] took pains to secure the services of the most distinguished artists and architects of the time in the building and adornment of St. Peter's and the Vatican, i.e., the papal church and palace. [Sidenote: The church of St. Peter.] The idea of the dome as the central feature of a church, which appealed so strongly to the architects of the Renaissance, reached its highest realization in rebuilding the ancient church of St. Peter. The task was begun in the fifteenth century; in 1506 it was taken up by Pope Julius II with his usual energy, and it was continued all through the sixteenth century and well into the seventeenth, under the direction of a succession of the most famous artist-architects of the time, including Raphael and Michael Angelo. The plan was changed repeatedly, but in its final form the building is a Latin cross surmounted by a great dome, one hundred and thirty-eight feet in diameter. The dimensions and proportions of this greatest of all churches never fail to impress the beholder with something like awe. [Sidenote: Height of Renaissance art.]