Citadel, << SIHT uh duhl or SIHT uh del, >> is a high, walled fortress built to defend a city. A citadel usually stands on a high hill overlooking a city. In early days, its walls surrounded the palace of the ruler.
The citadels of Mycenae and Tiryns in Greece were important ancient fortresses. The citadel known as Acrocorinth, built on a hill more than 1,800 feet (549 meters) high, guarded the Greek city of Corinth. The French citadel of Carcassonne was an important stronghold during the Middle Ages. The best-known citadel in North America stands atop Cape Diamond in Quebec, Canada. The French built it about 1665, and the British rebuilt it from 1823 to 1832.
