Over the years, the church was transformed from a basic Mannerist church into the most outstanding treasure. Throughout the centuries, every grand master and many knights donated gifts of high artistic value and made enormous contributions to enrich the church, with the best works of art by leading artists of the time.The church was intended to be a landmark that could be seen from almost anywhere on the island. The church was built by the Order’s military engineer and architect Gironimo Cassar (c. 1520-93). Its austere design reflects the sombre mood of the Order after the Great Siege.The façade is buttressed by two large bell towers topped with octagonal spires. The church is rectangular in shape with a wide nave, roofed over with a barrel vault. The oratory and the sacristy were built in 1604. The precincts also include a cemetery.