The walls of the atrium and round the doorways of the church show everywhere traces of fresco paintings of various periods, from Byzantine to Giottesque and the fifteenth century Lombard school, carefully uncovered in recent times, but all hopelessly ruined. The two large half-obliterated scenes in chiaroscuro on either side, at right angles to the front wall of the church, have been attributed tentatively to the little-known painter, Zenale. They represent the story of St. Ambrose and St. Augustine. That on the right hand, which is the least spoilt, shows three devotees kneeling before St. Ambrose, who are supposed to be the three successive dukes, Francesco, Galeazzo Maria, and Gian Galeazzo Sforza. On the left of the principal door, supported on four columns, is the sarcophagus of the humanist, Pier Candido Decembrio (died 1477), secretary and biographer of Duke Filippo Maria, and of his successor, Francesco Sforza. It is a graceful Renaissance work, perhaps by the Lombard sculptor, Tommaso da Cazzaniga,[11] and has bas-reliefs on the front, showing the Virgin, with Decembrio kneeling before her protected by St. Ambrose, and the journey of Tobias and the Angel, signifying the soul’s journey into eternity. A very archaic bas-relief representing St. Ambrose, with the triple-thonged scourge in his hand, is on the wall beyond the left-hand door. The atrium is a museum of sculpture of many periods. Here are monuments and shields of mediæval and Renaissance days—tombstones cast out from this and neighbouring churches—the broken original of the carven beasts over the right-hand door, and various unburied fragments of that dead Roman world which underlies Milan. Footnote 11: See Malaguzzi Valeri, _G. A. Amadeo_, p. 295. The great wooden door of the church, carved all over with small scenes, and of very ancient origin, has lost its interest by a too complete restoration. An unrestored fragment which is kept in the _Archivio Capitolare_ has been pronounced to be of the time of Theodosius.