from Wikipedia:
The once 20 Domus de Janas (rock tombs) of Sant' Andria Priu (Italian: Ipogeo S. Andrea Priu) are located in a 10-meter-high trachyte wall on the southern edge of the Campeda plateau near Bonorva in the metropolitan city of Sassari on Sardinia. The 15 preserved structures date from the Ozieri culture (around 3000 BC).