Construction of the Mother Church of the Holy Trinity began in the 14th century and was opened for worship in 1404. During the building process, a pre-existing Norman tower was incorporated into the structure and converted into a bell tower. Two dates are engraved on the tower — 1091 and 1115 — believed to mark the start and completion of the original construction.

The church features a single nave, measuring 50 meters in length, 10 meters in width, and 15 meters in height, with a Latin cross floor plan.

Side chapels open along the length of the building, which ends in a spacious apse.

Inside, the dominant material is yellow marble extracted from the Kassarquarries. The stuccowork is by local master Antonio Messina, a follower of the Serpotta school. His most prominent figures include God the Father, Our Lady of Sorrows, Saint John, and the Apostles Peter and Paul.

The main altar features the Holy Crucifix, dated 1301 and attributed to an unknown artist. In the presbytery, four statues are placed in elegant niches: Saint Simon the Apostle, carved in wood by Marco Lo Cascio in the 16th century; Saint Anthony the Abbot and Saint Francis of Paola, both 17th-century works by unknown artists; and Saint John the Apostle, also by Marco Lo Cascio.

Along the nave, a series of altars tells the story of centuries of devotion. Among them is the altar of Our Lady of Sorrows, made of fine walnut wood and housing the statue of the Virgin, who — according to tradition — wept in Castronovo in 1931. The Altar of the Three Wise Man, built in 1605, displays a painting by Pompeo Buttafuoco in 1604. Also noteworthy is the Madonna of the Rosary, a 17th-century painting by Vito D’Anna.

The marble immersion baptismal font, sculpted in white Carrara marble by Antonello Gagini in the 16th century, is accompanied by a 15th-century ciborium, also in white marble, by Domenico Gagini.

Continuing along the nave, visitors will encounter more altars and works that reflect centuries of devotion.

The altar dedicated to Saint Lucy, built in 1870 and restored in 1956, houses a statue from the early 20th century. A bit further on is the wooden statue of Saint Calogero, dated to the 17th century. The altar of the town’s patron saint, Saint Vitalis, features a 17th-century, while the Altar of the Holy Souls presents a vivid depiction of Purgatory.

Also present are the altar of Saint Joseph, with both an 1800s canvas and wooden statue, and the altar of Our Lady of the Chain, enriched by a white Carrara marble sculpture attributed to Antonello Gagini.

Among other notable artworks is Saint Peter Enthroned, also in Carrara marble; the wooden statue of Saint George carved in 1588; the processional float of the Annunciation; and the pipe organ with its choir loft, crafted by Raffaele Della Valle in the 18th century.

The sacristy is a spacious room decorated with stucco and well-executed paintings. In 1986, it was restored to house the parish museum. Among the most important works are a 14th-century ivory cabinet, a painting of Christ at the Column from the school of Rubens, and a Magdalene by an unknown artist from the Flemish school.