San Massimo's Church, situated in the historical center of Isola del Grasso, preserves on the back remains of the ancient fortified walls surrounding the town in the Middle Ages. The church has a precious stone portal dated 1420 and attributed to Matteo da Napoli (Matteo Capro). It opens on the right aisle of the church, which consists of a nave and two aisles by lancet arches lying on pillars. The middle nave ends in the high altar, located inside the apse and flanked with a beautiful wooden pulpit. The left aisle is dedicated to San Jacopo and houses a Renaissance baptistery dated 1529 and ordered by the first Marquis of the Sicilian Valley, Ferdinando Alarçon y Mendoza. The sacristy keeps a valuable fifteenth-century monstrance and a panel made up of fifteen majolica tiles painted by Andrea Pompei from Castelli in 1735, portraying the Madonna with the Child, San Berardo and Santa Colomba moved from a small hermit's church at the foot of Infornace Mountain. The external wall is characterized by the insertion of fragments of stone decorative sculptures. The belfry lies against left wall of the church and outstands with its unusual roundish pinnacle of oriental style.