This old, early Christian basilica is one of the oldest buildings in the city, built to house the relics of St.Vittore and St. Satiro. There are remains of the Oratorio of St. Martino ad Corpus (destroyed in 700), as well as the octagonal mausoleum of St. Gregorio, even featured in some views from the 16th century, which testifies to it's antiquity. The octagonal martyrium is also a prototype of the flourishing and vast spread of the ambrosian baptistry style. The building of the new olivetano complex began in 1508, while the church began to be rebuilt in 1560. It is difficult to say who designed it, views on this range from Galeazzo Alessi and Vincenzo Seregni. The incomplete facade offers formal solutions of great interest.
The ex-monastery of St. Vittore, rebuilt by the Olivetani in th 16th century is of interest, and it now houses the 'Leonardo da Vinci' Museum of Science and Technology in addition to being one of the most interesting monastic structures of the first half of the 16th century.