Since the 13th century, Sisteron has been a "bell-ringing, bell-tolling" town. The Cathedral bell summoning the faithful for the different services throughout the day according to the Liturgical Day (Call to Prayers at specific times of the day),
The Seven Canonical Hours of the Daily Office : Matins & Lauds, Prime, Tierce, Sexte, Nones, Vespers and Compline. The bells of the numerous local convents also rang out : Cordeliers, Antonines, Dominicans, Clarisses. In the 17th century, specifically in 1631, the bells of the Ursulines and the Visitandines, were also added.
The Cathedral of Notre Dame de Pommeris - from the Latin word "pomoerium" meaning "enclosed field or area" - became Notre Dame des Pommiers. Built in the 12th century, it was part of a larger episcopal group with the Church of Saint Thyrse and the Baptistry of Saint John the Baptist. The architecture of Notre Dame des Pommiers is typical of the Romanesque art of Haute-Provence. The dichotomy (architectural relationship between contrasting elements) of its facade and the vault of its dome indicates influences of Lombard Alpine art and architecture. The proportions of its single nave, with areas of barrel vaults, and framed by two narrow aisles, are reminiscent of the buildings of lower Provence. Its bell-tower has been altered many times. On the Romanesque base from the beginning of the 13th century, a second floor was erected in the 17th century, itself crowned with an octagonal pyramid in 1853. The Convent of The Visitation was originally a four-sided building set around an open promenade area (a square) with arcades (arched walkways). Today only the north wing and the chapel remain.