Layout
Fort Boyard is oval-shaped, 80 metres (260 ft) long and 40 m (130 ft) wide. The walls were built 20 m (66 ft) high. At the centre is a yard, and the ground floor provided stores and quarters for the men and officers. The floor above contained casemates for the emplacements of guns and further quarters. Above that were facilities for barbette guns and mortars.
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