Sacred and cosmically-aligned
The Santa Cristina archeological area in Paulilatino is a very nice and easily reached on the SS131 in Oristano. It's most famous for the Sacred Well of Santa Cristina, a structure so precisely-built that it seems impossible that it was actually built thousands of years ago. I'm not just talking about the stone staircase leading to the spring, either. I'm also referring to the fact that the entire structure is astronomically oriented. It appears to have been oriented in a way to coincide with the various phases of the moon.
The archaeological site includes other structures like a dolmen and a village, including a meeting hut where the chiefs of the ancient tribes came together.