Today Feriolo is a popular visitor centre, especially with campers, but its origins go far back into the past.

Nothing is left of the 12^th – 13^th century castle but a short section of the internal wall and the remains of the central tower, but there is no doubt as to the strategic importance of this place in Roman times. In those days, all border territories located at the mouth of a valley or an important artery of communication became part of a network of defence and control operations.

The Castle originally had two circuits of walls; the first, made of rows of well-shaped granite blocks, followed the contours of the rock on the upper part of the rise where the castle stands, while the second extended to the south. The tower, part of which is still visible, was nine metres high, built of granite on a square plan; in a prime strategic position, it could communicate with the tower of Mergozzo to the north and with the one on San Giovanni Island to the south.

These towers, along with the Fortilizio del Motto at Gravellona, formed an important line of defence between the two shores of the western gulf under Lombard dominion. Inside the building, the hearth and part of the chimney are still discernible in the wall.