The name means ‘ruins’, perhaps being those of the Roman village of Ghentiana, where the Byzantines built the Chiesa di San Teodoro. Ruinas is an agropastoral town with less than 700 inhabitants in the upper Marmilla region, in particular of the historical area of Brabaxianna (the gate of Barbagia), bordering Mandrolisai. It stands on a plateau 350 metres up, separated from Samugheo by the river Araxisi, a major tributary of the Tirso, which flows in a lush valley amidst tamarisks and rocky walls, forming various ponds. To the west of the village stands the imposing Monte Grighine, at almost 700 metres in height, a massive perhaps once dedicated to the worship of the goddess Diana, a symbol of virginity. Numerous springs arise here, including Santu Teru, Botta ‘e Corongiu and Abbadda, which render the territory particularly lush.