It is an important witness to the system of surveillance and defence of the Campidano territory in medieval times and it is also literally surrounded by fascinating legacies from pre-Nuragic and Nuragic times. The castle of Baratuli stands on the top of Olladiri in the territory of Monastir and was built on a previous settlement dating back to the Bronze and Iron Ages. It was built around the middle of the 12th century in the name of the judges of Cagliari, with the aim of monitoring the southern part of the Campidano area. It later passed to the Gherardesca family, who also owned the castles of Acquafredda and Gioiosa Guardia between the current territories of Siliqua and Villamassargia. After the fall of Count Ugolino, one of the most famous and controversial characters of Dante’s Inferno, it ended up in the hands of the Republic of Pisa, which destroyed it in the early 14th century, perhaps to avoid it being conquered by the Aragonese. Along with the castle, the village of the same name located in the valley, near the country church of Santa Lucia, was also destroyed.

By observing the foundations and the wall base of the fortress - a hexagonal layout with a paved courtyard in the centre - you will also see the remains of a barrel-vaulted cistern and other structures, probably used as storehouses and accommodation. On the other side of the courtyard, opposite the entrance, are the foundations of the main tower, which could be reached via a flight of steps. Beyond the courtyard, a furnace and traces of the curtain wall can be seen. From the castle, there is a 360-degree view, allowing you to see Monastir, as well as the towns of Ussana to the north, Serdiana and Dolianova to the east and Sestu to the south.

At the base of Mount Olladiri, next to the path leading to the top, you will notice cavities dug out of the basaltic rock: this is the necropolis of Is Aruttas, consisting of five Domus de Janas, dating back to between 3200 and 2800 BC. Four tombs are made up of an entrance, an anteroom and a burial chamber, while one of them was never completed and only has one room. Not far from the site are the remains of a pre-Nuragic settlement, after which a large Nuragic village was built with numerous huts. The surrounding area reserves other surprises: next to Olladiri, there is another mountain, Zara, on which you can see the ruins of a large settlement frequented between the pre-Nuragic age and the Roman period. There are two funeral areas, including a necropolis with two Domus de Janas, side by side, which, due to their unusual features, have been named is ogus de su monti, ‘the eyes of the mountain’. At the top, you will notice a monumental flight of steps, leading to a sacred area with altars and wells, while on the slopes of the hill there are traces of circular huts. This is where a sandstone artefact was found and some have identified it as a wine press, perhaps the oldest in the Mediterranean and an exceptional piece of evidence of wine production, a widespread activity in the Nuragic age. Today, it is kept in the council chamber of the Monastir town hall.