Nice photographs of a painted rock-cut tomb in Sardinia, apparently dating to the late Neolithic, 3800 to 2900 BC. Narrative here.
Sardinia has fascinating archaeology. Between about 1500 BC and 300 BC, when the island had been tied into Mediterranean trade networks but not yet absorbed by classical civilization, the islanders built dozens of stone towers called nuraghes.
A few of these were very elaborate, like the "nuragic palace" at Barumini:
The ancient Sardinians get a lot of play on new-agey web sites as a "mysterious ancient people," but really they were no more mysterious than any culture without written records. When trade and wealth came to the island, competition among the native elite intensified, leading first to very elaborate tombs and then to ever more elaborate fortresses. Eventually the Romans conquered them and they got a lot less interesting.