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.^[1] 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.