Concentric castle

A concentric castle is a castle with two or more concentric curtain walls, such that the outer wall is lower than the inner and can be defended from it. The layout was square (at Belvoir and Beaumaris) where the terrain permitted, or an irregular polygon (at Krak and Margat) where curtain walls of a spur castle followed the contours of a hill.

Concentric castles resemble one castle nested inside the other, thus creating an inner and outer ward. They are typically built without a central free-standing keep. Where the castle includes a particularly strong tower (donjon), such as at Krak or Margat, it projects from the inner enceinte.