Olbia is a coastal city in northeast Sardinia, Italy. It's known for the medieval San Simplicio basilica, and for cafes dotting central squares like Piazza Matteotti. On the palm-lined waterfront to the east, the Museo Archeologico di Olbia has exhibits ranging from Nuragic artifacts to Roman warships. The hilltop Nuraghe Riu Mulinu is an archaeological complex with views of the Gulf of Olbia.