The fortress was raised in the reign of Louis XIV, who built it here in the Dauphiné when France was at war with Italy. In the 12th century, a small stronghold existed, called castrum dulphin in Latin, fief of the count of Forcalquier. Building works began in 1694. In the nice reddish citadel, the building could house 2 000 men! In 1792, the fortress became Mont-Lion.