Porto Torres is a town in northern Sardinia, at the mouth of the Mannu River. It was a Phoenician, Carthaginian, and then Roman port. The Roman site features a well-preserved Roman bridge of the 1st century BC and Roman baths. . The Basilica of San Gavino (11th century) is one of Sardinia's most famous churches. Another highlight is an enormous stone altar that dates from 4,500 BC.