The Chiesa della Santissima Annunziata, a monumental church that occupies a large part of the hospital façade, overlooking Piazza Duomo. It traces its roots back to the mid 13th century when the bishop granted the hospital community the right to have its own oratory inside. Gradually developed along the front facing the cathedral, its exterior façade was decorated with Stories of the Virgin. Among the authors were Pietro, Ambrogio Lorenzetti and Simone Martini in the 1430s.
In the second half of the 15th century, the Church of the Santissima Annunziata was further transformed. The church was enlarged in height, a coffered ceiling was built and the apsidal area was decorated. The burial place of rectors and eminent members of the hospital community (some slabs can be seen today walled up in the hospital’s twentieth-century atrium), it was equipped with four side altars and the articulated high altar. It is undoubtedly a treasure trove of important works of art and furnishings. On the high altar, infitti, one can see the splendid bronze sculpture of the Risen Christ, created by Lorenzo di Pietro known as il Vecchietta for his own funeral chapel (never completed). Finally, the last monumental intervention can be considered the decoration of the large apse basin, painted with a representation of the Piscina Probatica in the 1730s by Sebastiano Conca.