The term CASTLE PARTS can be broken down into two crossword solutions: TOWERS (6 letters) and MOAT (4 letters). TOWERS are tall, fortified structures that were built as part of a castle's defense system. They were usually made of stone or brick and could be used to look out for enemies. A MOAT is a deep, wide ditch filled with water that surrounded the walls of a castle. It was designed to protect the castle from attack and to make it difficult for enemies to get close.