Complex sentence: They retained many of the external features that had become associated with nobility but with a larger ground plan, classically a "Z-plan" of a rectangular block with towers, as at Colliston Castle (1583) and Claypotts Castle (1569--88).
Split into simpler sentences: They retained many of these external features which had become associated with nobility, but with a larger ground plan. This was classically a "Z-plan" of a rectangular block with towers, as at Colliston Castle (1583) and Claypotts Castle (1569--88).