Serravalle is a castello located in the European republic of San Marino. With a population of 10,591 inhabitants (of that 2,000 are of foreign origin, 2006) and a surface of 10.53 km², it is not only the most densely populated municipality in San Marino, but it also contains its largest settlement (Dogana). Serravalle is located on the edge of the Apennines Mountains.