The history of Orco and its community started from the building of the fortified structure of an early medieval Castrum, a military center of power around which gravitated life.

The Castrum of Orco was part of the defensive system created by the Finalese's Marquisate (along with those of Pia and Perti) and was erected in an elevated and strategic position with defensive functions and for the control of the transits. Initially built of wood, the Castrum became a massive tower about 15 meters high, made of large stone blocks. From its foundations it is possible to enjoy a stunning panoramic view of the nearby Monte Cucco and the whole valley.

The stone tower of the Castrum of Orco never developed into a real castle: a few years after it was completed, in the late twelfth century, the Marquis decided to change their defensive strategy and began the so-called "decastellamento", which involved the progressive abandonment of military small existing fortifications. It was therefore decided to find a new city, surrounded by walls, in order to control the traffic coming from the sea: this change represented the birth of Finalborgo.