Smar Jbail was part of the crusader fief of Saint Montagne of the Lords of Batroun. The Crusaders built walls of bossed stone and rubble and surrounded the fortress with a rock-cut moat. Within the inner courtyard stands a central keep along whose north wall is a well preserved cistern covered by a pointed arch. The simplicity of its plan, which is similar in arrangement and appearance to the Byblos Castle, as well as the square tower, date this fortress to the early 12th century.