A fortified complex, built on the western hill of Affile and independent of the settlement then present on the hill that now hosts San Pietro, the first mention of which dates back to 1013.
At the end of the century the ownership was disputed between the Affile Lord and the abbey, which only managed to regain control of the castrum in 1176.
In a 13th C. fresco found in the cloisters of the Santa Scolastica Monastery in Subiaco, the castrum is depicted with two towers.
Yet in a second 15th C. representation found in the church of San Pietro, the castrum reveals a greater number of towers and is girded by powerful walls that encircle the inner inhabited nucleus.
Few traces are left today of the polygonal walls (“Porta della Valle” - Valley Gate) of the 14th C., with an advanced semicircular bastion; the risalit near the bell tower of Santa Felicita dating back to the 17th C. The sources also mention a “Porta Vipera” (Viper Gate).