The greatest fortress built by European crusaders in Syria and Palestine, one of the most notable surviving examples of medieval military architecture. Built at Qal'at al-Hisn, Syria, near the northern border of present-day Lebanon, Krak occupied the site of an earlier Muslim stronghold. It was built by the Knights of St. John (Hospitallers), who held it from 1142-1271, when it was captured by the Mamluk sultan Baybars I. It has two concentric towered walls separated by a wide moat and could accommodate 2,000 men. It is one of the few crusader castles to have been systematically excavated and restored.