Sinis is the area northwest of Oristano between Santa Caterina di Pittinuri, Cuglieri, Monte Ferru, Riola, Cabras and the sea.
The coastline alternates between limestone cliffs of Capo Mannu and Capo San Marco and the low, sandy shores such as at sa Mesa Longa, Pallosu, Is Arutas and s'Arena Scoada, with crystal-clear turquoise waters and beaches of a dazzling white due to the sand rich in quartz grains.
Offshore, facing the coast of Cabras, lies the uninhabited Island of Mal di Ventre, while a few miles further south lies the Scoglio del Catalano; but the main feature is the presence of a series of coastal ponds and saline, that contribute to biodiversity and represent the best habitat for many species of birds, both migratory and resident, among which there are the purple gallinule Western Swamphen (Porphyrio porphyrio), the Pink Flamingo (Phoenicopterus roseus), Black-Winged Stilt (Himantopus himantopus), the Cormorant (Phalacrocorax carbo), the Gray Heron (Ardea cinerea), the Yellow-Legged Gull (Larus michahellis) and many other species.
The vegetation in the more arid areas is characterized by Mediterranean scrub: wild olive-tree (Olea europaea sylvestris), Lentisk (Pistacia lentiscus), Arbutus (Arbutus Unedo), Myrtle (Myrtus communis) and Salvia Cistus (Cistus salvifolius); while, in the wetlands, it is made up of Willows (Salix fragilis), White Poplars (Populus alba) and Tamarisk (Tamarix gallica).
Finally Sinis is rich in sites of great archaeological and historical-cultural interest: the hypogeum of S. Salvatore, over 70 nuraghes including the S'Urachi one, the ancient site of Mont'e Prama’s Giants, the Phoenician-Punic city of Tharros, the early Christian church of San Giovanni di Sinis, the Spanish Tower of San Giovanni…