When he was twenty-six Ghirlandaio went to Rome to paint the Sixtine library, and then to San Gimignano, where he was assisted by Mainardi, who was to remain his most valuable ally in executing the large commissions which were to come to his workshop. His earliest Florentine frescoes are those which we shall see at Ognissanti; the Madonna della Misericordia and the Deposition painted for the Vespucci family and only recently discovered, together with the S. Jerome, in the church, and the Last Supper, in the refectory. By this time Ghirlandaio and Botticelli were in some sort of rivalry, although, so far as I know, friendly enough, and both went to Rome in 1481, together with Perugino, Piero di Cosimo, Cosimo Rosselli, Luca Signorelli and others, at the command of Pope Sixtus IV to decorate the Sixtine chapel, the excommunication of all Florentines which the Pope had decreed after the failure of the Pazzi Conspiracy to destroy the Medici (as we saw in chapter II) having been removed in order to get these excellent workmen to the Holy City. Painting very rapidly the little band had finished their work in six months, and Ghirlandaio was at home again with such an ambition and industry in him that he once expressed the wish that every inch of the walls of Florence might be covered by his brush--and in those days Florence had walls all round it, with twenty-odd towers in addition to the gates. His next great frescoes were those in the Palazzo Vecchio and S. Trinita. It was in 1485 that he painted his delightful Adoration, at the Accademia, and in 1486 he began his great series at S. Maria Novella, finishing them in 1490, his assistants being his brother David, Benedetto Mainardi, who married Ghirlandaio's sister, and certain apprentices, among them the youthful Michelangelo, who came to the studio in 1488. The story of the frescoes is this. Ghirlandaio when in Rome had met Giovanni Tornabuoni, a wealthy merchant whose wife had died in childbirth. Her death we have already seen treated in relief by Verrocchio in the Bargello. Ghirlandaio was first asked to beautify in her honour the Minerva at Rome, where she was buried, and this he did. Later when Giovanni Tornabuoni wished to present S. Maria Novella with a handsome benefaction, he induced the Ricci family, who owned this chapel, to allow him to re-decorate it, and engaged Ghirlandaio for the task. This meant first covering the fast fading frescoes by Orcagna, which were already there, and then painting over them. What the Orcagnas were like we cannot know; but the substitute, although probably it had less of curious genius in it was undoubtedly more attractive to the ordinary observer.