The Petralia Sottana Duomo, dedicated to St. Assunta is located in the old "Pusterna" quarter. This building did not have a precise origin, but through centuries its structure and its configuration, both on the inside and outside, has been significantly changed.

Of the original XV century plant remains only the side portal splayed, which still retains the Catalan Gothic taste relief decoration with thistle leaves and some art works housed inside. With the 17th century remodelation, the building appearance and size were entirely changed.

The bell tower

On the right side of the transept is located the white limestone bell tower, about 30 meters high, completed on 1680, as can be seen by an inscription on the tower attic.

The interior

The interior of the building is a Latin cross, divided into three naves: the central covered with barrel vaults and the side ones covered with groin vaults. The vaults are supported by six pairs of Tuscan columns extracted from Lumachella quarry, the so-called "Vazu Santu Tieru".

The church is a precious chest that contains priceless art works, here are the most important:

• Marble polyptych of Madonna Assunta made by Giorgio from Milano on 1501.
• XV century late Gothic wooden altarpiece from the Sienese school made by a Madonie unknown master.
• Oil on canvas San Mauro representation made by Giuseppe Salerno (Gangi cripple) on 1623.
• Oil on canvas Sant'Onofrio representation made by Giuseppe Salerno (Gangi cripple).
• XVI century sculptural group of the Nativitá made by Bartolomeo Berrettaro, Giuliano Mancino and Antonello Gagini.
• Oil on canvas representation of "cinque piaghe di Cristo" made by Giuseppe Salerno on 1629.
• XVII century San Calogero hermit wooden statue made by Brother Umile Pintorno.
• Oil on canvas representation of "Trionfo ed Eucarestia" made by Giuseppe Salerno on 1617.  
• XI century arabic bronze candelabra.
• Processional silver cross from XV to XVIII century.