Tertenia is the most southern village of Ogliastra, situated almost on the border of the Cagliari Province, at the extreme limits of what used to be  the medieval Judicature of Cagliari. The village is located on the slopes of Monte Giuilea, in a characteristic valley of tectonic origin which, from the pass of Genna’e Crexia stretches almost uniformly to the seashore of San Lorenzo, delimited to the west by the high limestone-dolomitic plateau of Taccu Mannu and Tacchixeddu , and to east of Serramarì that closes the view on the Tyrrhenian Sea to the village. In this valley, coming down from the Jerzu mountain, winds the river Quirra: This torrential stream represents the most important hydrological asset of the village and the entire area. The river is enriched along the way by numerous tributaries that create gorges and embedded meanders etching landscapes of unusual beauty.

The territory, mainly mountainous, faces the Tyrrhenian Sea along a 12 km coastline from Capo Sferracavallo to the village of Barisoni. Within this strip opens, a sort of natural amphitheatre, the gorgeous Sarrala plain to the west of the mountain chain of Serramari, forming a broad littoral stirred by various wine-red promontories and the splendid dunes of the whitest and finest sand. The long Tertenia coastline, with its rich hinterland, must have seemed an attractive landing place to remote sailors in search of favourable settling grounds.

The territory, varied, rugged and highly jagged, dominated by the dolomitic plateau of Taccu Mannu and Tacchixedda, is dotted with hamlets belonging to various municipalities, that originated in old times thanks to a donation made by the countess Donna Violante Carroz to the municipalities of the Sarrabus and Ogliastra regions; this is definitely a territory strongly characterised by its components.