Oristano, Oratory of the Holy Spirit

The oratory of the Holy Spirit is located in the historic center of Oristano, a short distance from the church of San Francesco and the cathedral of Santa Maria Assunta, in whose churchyard tombs from the 6th-7th century have been found, which, due to their radial arrangement around the building, are presumed to have been part of the cemetery of the Byzantine church.
Although there is a lack of reliable documentary evidence, it can be assumed that the church dedicated to the Holy Spirit, as well as the cathedral of Santa Maria Assunta, is also Byzantine in structure. The original title is unknown.
The analysis of the wall stratigraphy shows that the church has undergone different building phases, through which the system has been modified up to the current longitudinal plan. The plan of the original building can be assumed to be of a central type, probably cruciform. Some architectural and structural elements indicate a chronological location in Byzantine times, such as the wall walls outside the apse, in listed work, and the roof of the basin in tiles, with buttresses with concentric flounces.
In the eighteenth century, the church underwent heavy changes and is currently in sixteenth-eighteenth-century forms. By decree of Archbishop Giovanni Maria Bua, who had decided to demolish the nearby church of La Maddalena, the headquarters of the homonymous confraternity, established in 1594 by Pope Clement VIII, who governed it until 1958, was transferred there.

History of studies
The study of the building involved Renata Serra in 1971, who, in favor of the thesis of the primitive Byzantine structure, draws comparisons with a church in Basilicata, Sant'Angelo a Monte Raparo, which also has an apse with a concentric roof.

Bibliography by
R. Serra, “The Oratory of Souls in Massama, with reliefs of the monument edited by Augusto Garau”, in Annals of the Faculty of Letters, Philosophy and Magisterium of the University of Cagliari, Cagliari, XXXIV, 1971, pp. 33-56;
P.G. Spanu, Byzantine Sardinia between the 6th and 7th centuries, series “Late Antique and Medieval Mediterranean. Excavations and research”, Oristano, S'Alvure, 1998, pp. 61-63;
A. Pillittu, Archdiocese of Oristano, series “Churches and Sacred Art in Sardinia”, V, Cagliari, Zonza, 2003, p. 166;
R. Serra, Studies on the Art of Late Antique and Byzantine Sardinia, Nuoro, Poliedro, 2004, p. 51; R. Coroneo, Romanesque Churches of Sardinia.
Tourist-cultural itineraries, Cagliari, AV, 2005, p. 75.