Castiglione Olona is a town and comune in the province of Varese, in Lombardy. As of 31 December 2015, it has a population of 7,753 inh…Castiglione Olona is a town and comune in the province of Varese, in Lombardy. As of 31 December 2015, it has a population of 7,753 inhabitants. The area of the town with the greatest tourist attractions is the historic center.