Pembroke Castle is a structure that is fortified.
A castle ( from castellum ) is a type of fortified structure built in Europe and the Middle East during the Middle Ages by European nobility . This is distinct from a palace , which is not fortified ; from a fortress , which was not always a residence for nobility ; and from a fortified settlement , which was a public defence -- though there are many similarities among these types of construction . Pembroke Castle ( Castell Penfro ) is a medieval castle in Pembroke , West Wales . In 1093 Arnulf of Montgomery built the first castle at the site when he fortified the promontory beside the Pembroke River during the Norman invasion of Wales .