Castle of San Terenzo, Military museum castle in Lerici, Italy

Castle of San Terenzo is a fortification with stone walls built on a promontory overlooking the Gulf of La Spezia and includes a square defensive tower. The structure combines different building phases and contains multiple rooms now used for museum displays.

The castle was built in 1360 by the inhabitants of San Terenzo themselves, without artillery, ladders, ammunition or guards, as a document of 29 July 1588 in the State Archive of Genoa confirms. It began as a single square watchtower about ten metres high with merlons, then gained an irregular pentagonal wall with three circular lookouts and, on the landward side, a barbican facing a moat, now filled but recalled by a loophole in the north bastion. It later served as a defensive complement to the larger fortress of Lerici.

The castle's name comes from the village of San Terenzo, and the rocky inlet beneath it is called the Tana dei Turchi, the Turks' den, after the Ottoman pirate raids the fortress was meant to repel. Among its first castellans was Giovanni da Mongiardino, who commanded eight crossbowmen in 1401.

The best approach is via a steep footpath that requires physical effort and good footwear for the climb. Parking is limited nearby, so arriving early in the day makes the most sense.

During World War II, German forces occupied the structure and installed surveillance equipment to monitor ships moving through the gulf. Traces of this wartime function remain visible on site today.