Torre della Linguella, Coastal tower in Portoferraio, Italy

Torre della Linguella is an octagonal brick tower at the northern end of Portoferraio's bay, built in 1548 on the remains of a Roman villa. Its lower base rests directly on the rocky shore on six of its eight sides, while the upper section projects outward and ends in a terrace supported by stone brackets. A small circular structure sits at the center of the terrace, invisible from outside.

Built in 1548 by the Medici on the remains of a Roman building near the Villa della Linguella, the tower guarded Portoferraio's harbour and also stored salt. In the second half of the 18th century the Lorraine grand dukes turned it into a prison, which closed after the late 19th-century opening of the larger prison in Forte Longone at Porto Azzurro. The anarchist Giovanni Passannante was held here from 1879 to 1889.

Locals still call it Torre di Passannante, after the anarchist Giovanni Passannante, held here from 1879 to 1889 in conditions that left him physically and mentally weakened. The bandit Carmine Crocco also spent part of his imprisonment in the tower, and Sandro Pertini was confined here twice in 1933 and again on 9 September 1935 before being sent to Ponza.

The tower stands at the northern tip of the Portoferraio roadstead, with six of its eight sides resting directly on the rocky shore, so it is reached on foot along the waterfront. A lighthouse fitted by the Marina Militare on the western corner of the walls, now powered by a photovoltaic panel, marks the spot. The octagonal plan and the brick facing are visible from outside at any time.

The tower's upper terrace, ringed by stone brackets, holds a small circular structure at its centre that cannot be seen from outside the complex. The site also preserves the remains of the Roman Villa della Linguella beside the tower, and a 60 W rhythmic lighthouse on the west wall now guides the Portoferraio airport area at night.