In the protected natural area of Chia, in the municipal territory of Domus de Maria, is the locality of Capo Spartivento. Inland, a few kilometres from the coast, are the ruins of an ancient semaphore station dating back to the second half of the 19^th century. The building is located near the summit of Monte Sa Guardia Manna at 176 metres above sea level, where there are the remains of a nuraghe. From here, the view sweeps 360 degrees and opens onto the bustling southern coastline with Capo Teulada and Capo Malfatano in evidence.

The complex is today in a complete state of abandonment and consists of a rectangular building, about 10 metres long, resting on a rock and concrete base with an access staircase. The walls are made of squared blocks of sandstone covered with lime mortar. The entrance with a wooden door faces south-west. On the western side are two large arched windows with grilles. Inside one can still see the iron ceiling beams and two main rooms, in one of which there was a kitchen-oven. The upper terrace was accessible through an internal trapdoor and an iron staircase. On the right side of the building one can see the remains of a round-shaped watchtower, made of clay bricks and collapsed a few decades ago.

The maritime traffic lights had the task of regulating ship traffic. For the most part, they were built by the Regia Marina (Italian Royal Navy) between the mid-19^th and early 20^th century. They were used to communicate with vessels using a variety of signals with poles and flags.