In 963 a diploma of Emperor Otto I of Saxony names the castle of Trebiano: the first documentary proof that it existed, though the building itself is traced to the 10th century or a little earlier. Both a stronghold and a bishop's residence in feudal times, it stands on the hill above the medieval village of Trebiano, today a hamlet of Arcola, where the lower Val di Magra opens towards the sea. From up there two decisive trading harbours were kept under watch: Lerici, used above all by the Republic of Genoa and by France, and San Genesio, towards La Spezia, the hinge of trade with Tuscany.
What to see
The castle has not a single window. In their place run long, narrow arrow slits cut into a curtain wall that reaches 20 metres in height: this was a place for looking out, not for leaning out. The plan is square, or more precisely sub-pentagonal, and four large corner towers are absorbed into the curtain rather than projecting as separate volumes.
Ownership tells a border story. The castle first belonged to the Diocese of Luni, which held the feudal lands between Liguria and today's Lunigiana, and served as a bishop's residence: it stayed with the diocese even when, in 1039, the village passed to the first Lords of Trebiano, who were themselves close to the bishops of Luni. In the 13th century it entered the orbit of the Republic of Genoa. In 1442, during one of the many upheavals of Genoese politics, it was taken by Antonio Biassa, a member of a noble family from La Spezia.
Visiting
Trebiano is reached by car from the Arcola plain along a narrow climb that ends at the edge of the village; the last stretch is on foot, up stone lanes running between the houses. Do not expect a museum route: what survives is the defensive machine, and the reward is the sweep of the Val di Magra and the sea. Wear proper shoes, because the gradient is real and the paving uneven.
Our editors' tip
We go up in late afternoon, when the low light rakes across the arrow slits and the valley floor catches fire. First, though, we look at the castle from below, from the plain: from there you understand why it was planted here and nowhere else, watching the road, the river and the route to Lerici all at once. Then we keep a quarter of an hour for the walk around the outside of the walls, the best part of the climb.