Built in the twelfth century in an area outside the circle of walls, the Jerusalem hospital and the nearby church of the Holy Sepulcher were the seat, from its construction until 1798, of the Order of the Knights of Jerusalem also known as the Knights of Malta. In the fourteenth century it held the function of Grand Priory of Lombardy which was responsible for controlling the Order in northern Italy. The complex consists of a series of buildings. The round church was built between 1110 and 1130. Its original dedication to the Holy Sepulcher and its shape place it among the most significant examples of churches built in imitation of the rotunda of the Holy Sepulcher in Jerusalem.
 
The square-shaped Valperga chapel was built between 1446 and 1467 at the behest of the prior Giorgio Valperga and is characterized by notable terracotta friezes attributed by Francesco Filiberti of Alessandria. The cloister, with circular pillars and cross vaults with a perfect wall texture, took on an appearance very similar to that of today only in the 15th century. The rooms of the priory house are almost entirely the result of the intervention of 1930-31.
 
The Archaeological Museum has been located in the San Pietro Complex since 1932. Consisting largely of four collections donated by citizens of Asti between the late nineteenth and early twentieth centuries, the Museum includes pre-Roman metals, Greek, Magna Graecia and Etruscan ceramics, and a substantial collection of Roman finds: terracotta pottery and oil lamps, cinerary urns, glasses, bronzes. Part of the Roman materials comes from grave goods from 1st century AD tombs. found in 1879 on the western outskirts of Asti. In the small but significant Egyptian section there are two mummies, the relative anthropomorphic wooden sarcophagi, canopic vases and a collection of amulets, ushàbti, statuettes of divinities and other objects of a religious-funerary nature.