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Heritage classified

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Origin and history

The tower of Cesson was built between 1395 and 1407 by order of Duke John IV of Brittany, succeeding earlier fortifications possibly dating back to the Gallo-Roman period. Placed on a rocky spur 70 metres above Saint-Brieuc Bay, it was tasked with controlling the mouth of the Gouët and monitoring maritime traffic, while protecting the city from pirate attacks. Its thick three-metre walls housed a spiral staircase and four floors, topped by a mâchicoulis platform. The tower was integrated into a vast castle, now extinct, whose remains include dry ditches and bastions adapted to artillery in the 16th century.

During the War of the League (1588–98), the tower of Cesson played a major strategic role, passing from the hands of the leaguers, led by the Duke of Mercœur, to those of the royal troops of Henry IV. In 1598, after a three-week siege led by the Brissac Marshal, the fortress was dismantled by royal order, although part of the tower was preserved as bitter for navigation from 1625. Materials from its destruction were partially used to bridge the ditches, while its ruins became an essential maritime landmark for the bay's navigators.

In the 19th century, the tower was acquired by Alexandre Olivier Glais-Bizoin, who built there a mansion and a park. Ranked and then declassified from the Historic Monuments in 1888 at the request of its owners, it was finally registered in 1926. During World War II, the Germans occupied the site to build bunkers, changing its landscape in a sustainable manner. Today, the tower and its estate, bought by the city of Saint-Brieuc in 2020, are being restored and opened to the public, after decades of abandonment and arson in 2018 that damaged the adjacent mansion.

The excavations and toponymic studies reveal that the castle of Cesson, whose tower is the last vestige, extended over about 3 hectares and included a lower courtyard, casemates, and a chapel dedicated to Saint Maurice. The archives also mention his role as a prison in the 15th century, as evidenced by the imprisonment of Morice de Ploësquellec in 1423. The tower, built of stone and stone cut connected to lime, illustrates the Breton military architecture of the late Middle Ages, with its dust bays, chimneys, and defensive system adapted to the progress of artillery.

Cesson's site, which was occupied in ancient times, was also an issue during the conflicts between Britons and English. In the 14th century Olivier de Clisson and Jean IV de Montfort clashed for his control, reflecting the political tensions of the War of Succession of Brittany. The tower, a symbol of ducal power, housed the coat of arms of John IV and his wife Jeanne of Navarre, who had now disappeared. Its history thus reflects the strategic and political changes of Brittany, from its role as seigneurial residence to its purely military function under Henry IV.

Finally, the Cesson Tower embodies the challenges of heritage preservation. Its recent acquisition by the city of Saint-Brieuc marks a step towards its valorisation, after centuries of transformation and degradation. Current projects aim to make this emblematic monument accessible, while preserving the archaeological remains of its fortified past, bearing witness to nearly six centuries of Breton and maritime history.

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