The Stazione Centrale in Cagliari is next to the bus station on Piazza Matteotti. There are fairly good connections between Olbia, Cagliari, Sassari, and Oristano. Service on the few other local lines is infrequent and slow. The fastest train between Olbia and Cagliari takes nearly four hours. Local trains connect Sassari with Alghero (one hour).
If you can stand a little agitation, consider taking a trip on the rickety old single-gauge railroad that runs between Cagliari and Arbatax, midway up the east coast (with a change at Mandas). The line has been operating since 1893; it takes about seven hours to cover the approximately 250 km (155 miles) of track, with daily departures in summer. The train rattles up into the Barbagia district through some breathtaking mountain scenery, then eases down into desert inland landscape before arriving at Arbatax, where the trip ends on the dock next to the fishing boats.
Ferrovie dello Stato (892021 in Italy; +3906/6847 5475 outside Italy. www.trenitalia.com.)
Trenino Verde della Sardegna (070/265 7622. www.treninoverde.com. June–mid-Sept.)