Castel Seprio - in the province of Varese - was built in the early fourth century AC, following the barbarians invasions (in the third century the barbarians started to heavily cross the Roman empire boundaries of  the center of Europe and in 269, the Alamanni had come to Milan) as a military post along the way Como -Novaria to defend the boundaries (Iimes) on this side of the Alps.  Belonging to  this period belong three towers are still visible at the level of the foundation, on the plateau of the castrum.
The history of the ancient area takes place from late antiquity to the end of the XIII century  through the domination of the Goths and the wars Goths-Byzantium, Longobards  rule (VI-VIII century) and Carolingian age (end of the eighth century ...).
The fortress was destroyed after years of attempts, during the night of March 28, 1287, at the conclusion of the struggle for the conquest of the Lordship of Milan between the families Della Torre (defeat) and the Visconti family (winning): the military and civilian buildings were completely destroyed. The archbishop Ottone Visconti decreed that never the ancient fortress  should have been rebuilt again and the place should have been an uninhabited place.
 Every year up to 1786  the captain and the vicar of Seprio  took an oath to enforce the ban, and this was widely respected (it was suppressed by the Austrian Emperor Joseph II).
From  the destruction only few building were saved: churches with their service houses and their  remains are visible within the current archaeological zone. Since then the place was no longer inhabited except by the religious. He was also abandoned by them at the end of '500.
Declared June 26, 2011 a World Heritage Site by UNESCO in seven Italian sites related to Longobard civilization.
Currently these monuments can be visited : the bridge, the walls, the towers, the church and the convent of San Giovanni, the houses, the church of St. Paul, the Church of St. Mary and the Monastery of Torba.