Officially designated as a Sanctuary on October 18th, 1985, the Church of Santa Maria delle Grazie, originally dedicated to Saint Saturn was probably built between the end of the 12th and the beginning of the 13th century.
The façade is divided into two levels. The first, dating back to the 13th century, enframes the portal with a lintel sculpted in acanthus spirals, surmounted by a round arch that bears an inscription with the coat of arms of Canon Marco Canavera from Iglesias. The second level features a Gothic-style single window, while the upper part, where two windows open, was built in the 17th century and ends with a broken pediment and a sail-shaped bell tower, one of which shows an effigy of Saint Catherine of Alexandria and the date 1649.
The interior has a single aisle layout with a wooden roof supported by five pointed arches. In the second bay, on the left side, there is a grille with a small door used for the Holy Communion of the Clarisse nuns from the adjoining monastery, which was later suppressed. On the right wall of the fifth bay, at a low level, there is an embedded funeral inscription in memory of the Capuchin priest Benedetto from Iglesias, who died in 1713. In the last bay, two small side chapels open up, one dedicated to Saint Francis on the left and one to the Sacred Heart of Jesus on the right.
On the back wall, there is the seventeenth-century wooden statue of Our Lady of Grace, venerated by the community of Iglesias for having freed the city from the plague of locusts in 1735.
The Celebration of Our Lady of Grace is celebrated on the second Sunday of July every year. During the Eucharistic celebration, the Mayor of Iglesias, on behalf of the Municipality and the people of Iglesias, renews the ancient vow to the Madonna by rereading the Supplication and offering a candle as a thanksgiving for the liberation from the voracious locusts, which had devastated the fields for twenty years, plaguing a population already afflicted by drought and pestilence.