The fortification that was set forth and enlarged during previous centuries stopped taking shape during the 19th century. Prior to the start of the conflict, the hill’s southeastern curtain wall had already been lengthened until the Tongue of the Serpent and a rammed earth wall had been built in the bastion of the King who divided it into two halves.
During the conflict it was necessary to repair the damage that the explosion of the arsenal inside the Castle of the King caused in 1812. However, the most notable action from this period was the construction of the western end of the citadel with a new wall that joined the Diamond Point and the Tongue of the Serpent. The Lion's Gate, halfway between a bastion and another, was from 1826 the new entrance to the citadel.