The alternation of austere black-purple basalt of the walls and of dynamic pink trachyte in the arches and columns forms a unique two-tone that renders it mysterious and fascinating. From its vantage point atop a knoll in an isolated yet prominent position, the church of San Nicola stands above the village of Ottana, in the heart of the island. It was constructed in the Pisan-Romanesque style on the site of a pre-existing early medieval building, as was confirmed by burials discovered during excavations. The date of consecration (1160) is ‘branded’ on a parchment found during the restoration of the main altar. The imposing building was the cathedral of the Ottana diocese from 1112 until 1503, when the site was suppressed and transferred to Alghero. In much of the interim, between the institution of the diocese and the completion of the works, the nearby San Giovanni di Orotelli took on the role of cathedral.