Located between the upland and the valley of the River Olona, Castrum Sibrium was a military stronghold in Roman times and used over the following centuries by the Goths, Byzantines, Longobards and then the Visconti. Ottone Visconti, Lord of Milan, ordered the demolition of Castelseprio in 1287, with the exception of the religious buildings. One of these was the Church of Santa Maria Foris Portas (Latin for ‘outside the gates’) that was built between the fifth and ninth centuries.