Built in 1101 as a chapel of the Knights Templar and dedicated to St. John the Baptist, in 1314 it was granted by Frederick III of Aragon to the Augustinian fathers. They enlarged it by adapting it to the Gothic style and built an adjoining convent. Still remaining of the original structure are its gabled façade, its portal with pointed arches and a large rose window. Over the portal, in a niche, stands a Gagini-style sculpture depicting the Madonna and Child (sec. XVI).
The rose window of clear Chiaramonte Gothic style (14th century), much altered over time, was built with local stone from the ancient quarries at Pietretagliate. It is formed by intertwining arches on slender columns converging in the ‘Agnus Dei’ (God’s Lamb), the focal point of a Christological omen, creating a graceful and dynamic movement.
The church, which in the 16th century belonged to the city Senate, was closed as a place of worship in the 19th century and then radically changed.
The bombings of 1943 destroyed the apse and part of the nave, later reconstructed.
Having been given the function of auditorium it is now used as an exhibition space for the diocesan museum.