The Castelseprio Archaeological Park includes the remains of a castrum which developed in the 5th century AD on military pre-existences from the 4th century AD, with the parish church of San Giovanni and residential and service buildings. The castrum is surrounded by mighty turreted walls, which also defend the outpost at the bottom of the valley known as the Torba Monastery. Outside the walls are the village and oratory of Santa Maria foris portas, one of the most singular and important monuments of the early Middle Ages for the exceptional pictorial cycle of the eastern apse.