Sardinians call them domus de janas, houses of the fairies, and when you crouch at the entrance of one you understand the name. They are tombs cut straight into the soft limestone by the island's Neolithic and Copper Age people, small chambers linked by low doorways, sometimes with carved false doors or bull horns on the walls. The necropolis of Su Crucifissu Mannu, just inland from Porto Torres, holds a couple of dozen of them scattered across a low rocky plateau among fields and scrub, one of the largest groups in the north of the island.
The site feels wonderfully unbothered. There are no crowds, just lizards, the scent of wild fennel and the drone of insects, and the openings in the rock look like the doors of a tiny underground village. Bring a torch if you want to peer inside. The people who carved them lived long before the nuraghi, the stone towers that are Sardinia's trademark, and their tombs are among the oldest monuments on the island.
Porto Torres, five minutes away, was the Roman colony of Turris Libisonis, and its remains include baths and a bridge. Its great treasure is the basilica of San Gavino, the largest Romanesque church in Sardinia, built of pale stone on the site of the martyrdom of three Roman soldiers. The town is also the port for ferries to the mainland and for boats to Asinara, the long island off the northwest tip that was a prison for decades and is now a national park famous for its little white donkeys.
The riding nearby is a mix. The SS131 dual carriageway links Porto Torres with Sassari and the south quickly but without charm. Much better is the road west towards Stintino, flat and fast along the coast past salt pans and lagoons, ending at La Pelosa, a beach with water so pale and clear it looks unreal; in summer access is limited and traffic heavy. Inland, the minor roads towards Sorso and the Nurra have gentle bends through vineyards and olive groves. The mistral blows hard on this coast, and can make the bike work.
Porto Torres has fuel, supermarkets and plenty of places to eat. Try the local seafood, or a plate of malloreddus, little ridged pasta. Spring and autumn are best for riding; midsummer brings heat and tourists in equal measure.