The church of San Gemiliano, known locally as Santu Milanu, stands in the countryside of Sestu on a site that has hosted an Aeneolithic settlement and the Susue villa, dating from 1316-22. The church is dedicated to San Gemiliano and is a place of important devotion, with an enclosure that includes shelters used during the feast of the saint. The structure features 17th-century rooms on the north side and a 16th-century portico on the façade, characterised by powerful ogival arches.
The church is made of medium-sized limestone ashlars, and may have been built by the Victorian monks of Marseille in the 13th century, following the French Romanesque style, characterised by lobed arches, elongated corbels and 'accordion' pilasters found in the extension of the church of Santa Maria di Bonarcado and in the Cathedral of San Pantaleo in Dolianova, one could therefore hypothesise that the workers who worked in Sestu were trained in the latter.
The building has a longitudinal hall divided into two naves with separating arches and barrel vaults, each with an entrance on the façade and an apse; the northern nave is larger and has an apse divided into three by pilasters.