The town is located about 15 km East-North-East from Cagliari, on the first hilly hills of the western slopes of the Serpeddì-Sette Fratelli Massif.
The current forms of the Santa Barbara parish church are the result of various overlaps and additions that the church had to undergo over the centuries. Of the original structure, traced back to the type of the Sardinian-Catalan Late Gothic period, dating back to around the middle of the 16th century, the single-aisle structure with a pointed vault punctuated by six sub-arches, and side buttresses, including at different times the chapels were opened.
In the inventory drawn up in 1591 on the occasion of the pastoral visit of the Archbishop of Cagliari Delvall, the chapel of the Souls of Purgatory is mentioned, which, generally, was located at the base of the bell tower: this suggests that at that date even the bell tower, on the right in line with the façade, already existed, as evidenced by a document from 1616 in which it is said that it was now old and dangerous.
The building is characterized by the presence of two transepts: the result is a cross-shaped plan with two arms of different lengths. The first transept was built at a time very close to that of the late Gothic foundation; the second, with longer, wider and taller arms than the first, was completed by 1641, as evidenced by an inscription engraved on the drum of the large dome that rises at the intersection with the choir's arm. The transition from the quadrangular shape of the presbytery to the octagonal shape of the dome is allowed by four Catalan-style junctions (ribbed and gemmed half-vaulted cross vaults); the arms of the transept and the apse have a barrel vault. The triumphal arch that leads to the presbyterial area is decorated with geometric patterns alternating with floral motifs. The light that enters through the eyes of the dome illuminates the environment.
The diversity of the openings and roofs of the chapels testifies to the different moments in which they were built: about the last quarter of the 16th century, the first on the right (under the bell tower), with a rounded entrance arch and a cross vault with curtain shelves decorated in a wavy leaf; in the 17th century, the second and fourth on the right and the sixth on the left, all with a pointed arch and with a barrel vault except for the fourth on the right, which turned into a ribbed cross and a pendulous gem in the keystone of 1870; Go back to first chapel on the left, with an ogival arch and barrel vault while the remaining ones (3rd and 5th on the right, 2nd, 3rd, 4th, and 5th on the left) date back to the 18th century, all have a round arch opening and a barrel roof.
The neoclassical façade is divided by four pilasters into three mirrors, the central one of which, inside which is the lunetted portal, is framed by pairs of pilasters supporting a triangular tympanum. In 1962, the entire façade and part of the bell tower were covered with travertine, and a statue of Santa Barbara was placed in the pediment.
The square-shaped bell tower, rebuilt in 1870, is spread over three orders. The second, with rounded corners that form the base of four columns, houses the bells and ends with a high parapet. At the peak, an octagonal domed drum is set up. Along the sides of the church, the buildings of the chapels and the arms of the transept protrude.

Bibliography
R. Serra, “The parishes of Assemini, Sestu and Settimo San Pietro. Notes for a history of late Gothic architecture in Sardinia”, in Proceedings of the XIII Congress on the History of Architecture. Sardinia, I, Rome, 1966, pp. 225-243;
A. Anedda, Sinnai and its churches. Historical and artistic guide, Cagliari, Tea, 1982;
M. Corda, Arts and crafts in Spanish Sardinia. Archival documents, Cagliari, CUEC, 1987;
M. G. Scano Naitza - F. Virdis, “New documents for the parish church of Santa Barbara di Sinnai and considerations on some wooden statues in southern Sardinia”, in Aristeo. Notebooks of the Department of Archaeological and Historic-Artistic Sciences of the University of Cagliari, I, n. 1, 2004, pp. 295-315;
C. Perra, History of Sinnai from its origins to 1960, Sinnai, Su Fermentu Cultural Association, 2005;
A. Pistuddi, “Parish Church of Santa Barbara, Sinnai”, in The Jewels of Religious Architecture, Dolianova, Graphic by Parteolla, 2005, pp. 249-265.