The museum occupies space inside the old palazzo of Gallipoli's seminary which is adjacent to the Cathedral Basilica whose construction began in 1750.

The structure has substantially preserved its original look and, with the numerous Baroque decorations, covers 900 square meters laid out on three floors.

The statue of Saint Agatha (patron of the diocese and the city, as well as of the cathedral) " … was brought to Gallipoli on June 10, 1760 aboard xebecs at the expense and for the devotion of Msgr.

Oronzo Filomarini, precious liturgical vestments, and a 16th-century copy of the Holy Shroud, one of only five in existence (donated by bishop Sebastiano Quintiero Ortiz and made in direct contact with the original in Torino).

The archives include manuscripts related to pastoral visits, diocesan synods, bishops, excommunications, criminal trials, marriages, curial legislation, parishes, confraternities and monasteries, ordinations, patrimonies, charity, and private oratories.