Caslano is a municipality in the district of Lugano in the Swiss canton of Ticino, near to the Italian border. The center of the village is built within a Roman era fortification. While no trace of the actual fortification still exists, local tradition, the use of Castellano in place names and the compact structure of the once walled enclosure all indicate that the fortress existed. The hamlet of Torrazza was the source of bitter fighting between the Swiss Confederation and the Duchy of Milan. In 1604, the Treaty of Varese decided against the Italian municipality of Lavena Ponte Tresa and finally awarded it to Caslano.