The cemeterial basilica of San Calocero, located on the slopes of Mount San Martino, near the route of the ancient Roman road Iulia Augusta, is one of the oldest and most important testimonies of the spread of Christianity in Albenga and in western Liguria. According to tradition, Calocero, a soldier of Brescia origin, converted to Christian worship was allegedly martyred at the ancient mouth of the river Centa and then buried on the hill of Monte, in a site previously used as a pagan necropolis. The presence of the martyr's body made the area a place of worship and already between the 5th and 6th centuries. a church was built, which was later enlarged and brought to three naves. The San Calocero complex then passed under the control of the Gallinaria monastery, as evidenced by the inscription of the abbot Marinaces, from the early 8th century. Marinaces probably rediscovered the relics of the saint and provided for a new and more decorous arrangement of the same, inside a ciborium or an iconostasis of which numerous elements have been recovered, including the inscription itself.
A new arrangement of the martyr's bones, placed in a marble tomb under the central altar, will be carried out by the abbot Giovanni di Diano in 1286. In 1368 the Benedictines ceded the entire complex of San Calocero to the Diocese of Albenga who assigned it as the seat of the Benedictine nuns, who were later replaced by the Augustinians and finally the Poor Clares. With the transfer to the city of the latter, and of course of the relics, which took place in 1593, a long period of abandonment began for the area. The first archaeological excavations, conducted by Nino Lamboglia, began in 1934 and since then numerous campaigns have taken place which have highlighted the different phases of the complex and the use of the different rooms identified. The most recent interventions have also made access by the public possible.