The sacristy of St. Helena, spacious, bright and equipped with a beautiful pavilion vault, was built in 1815-18 during the rebuilding of the parish church on the pre-existing factory.
In addition to the traditional marble basin (1815-18) and the customary wooden paratora (1784), it houses numerous oil-on-canvas paintings from the 17th to 19th centuries, some of them from the former Capuchin convent of St. Francis, adjacent to the medieval church of St. Agatha, and the branch church of Saints Ephisius and Sebastian.
Of particular interest are: the Turritan Martyred Saints Gavino, Proto and Januarius (17th cent.), the Death of St. Joseph (18th cent.), twelve canvases, within polylobate frames, depicting episodes from the Bible (18th cent.), St. Catherine of Alexandria (18th cent. 18th cent.), the Virgin of Lightning Protecting the Village of Quartu (18th cent.), a Sacred Heart of Mary (Antonio Caboni, 19th cent.) and the Portrait of Canon Giuseppe Murgia, executed by Giovanni Marghinotti around the mid-19th century.
