Protected by the rocky spur on which the picturesque medieval village of Posada is set surmounted by the spectacular Fava Castle, Su Tiriarzu is one of the largest and most beautiful beaches of the Baronia sub-region, immersed in an uncontaminated natural setting. Its wide and long expanse of clear sand, fine and deep, is punctuated by sea lilies, facing calm waters whose shades range from blue to green, backdropped by luxuriant vegetation on the banks of the Tondu and Longu basins and by the mouth of the Rio Posada, whilst the Montalbo arises majestically and clearly in the distance.

The beach is the southernmost part of a four-kilometre sandy stretch, which takes various names along its wide and straight course, being just three kilometres from the town. Upon descending down the limestone walls on which the village arises, a path will lead you to the beach along a wooden bridge. The beach, which takes its name from tiria, a type of broom that grows in the greenery near the sand, is equipped with all services, including bathing equipment and pedal boat hire. Nearby there are hotels, camping areas, bars and restaurants. Its winds render it the perfect destination for surfers, also being ideal for snorkelling and underwater fishing enthusiasts.

Like Su Tiriarzu, the other beaches of Posada are a short distance from the village, all extending along the low coast formed by the mouth of the Rio Posada. To the left of the beach, the view is encircled by a sand dune arch surmounted by a low, round hill. On the right is the tower of Posadina di San Giovanni, next to which extends the San Giovanni beach. Further south is La Cala and, in the background, Santa Lucia, being the seaside areas of Siniscola. Heading north are the beautiful beaches of Orvili and Iscraios. Behind Su Tiriarzu there is an initial stretch of dunes and a pine forest, followed by the lagoon area alternating with Mediterranean scrub and consisting of a river delta and ponds interconnecting with each other and with the sea, forming the habitat of various species of birds, including pink flamingos.