Construction of this stronghold, which dominates the entrance to Lorient harbour, was undertaken in 1590, during the Spanish occupation. It has a rectangular form with bastions in each corner. On the sides, two bridges and a ravelin protect it from invaders. A signposted pathway takes you to the rampart walk and the two courtyards, the crypt and the Citadel museums (the French East India Company Museum, Sea Rescue Centre, Ocean Treasures, Maritime Museum and Armoury Museum).