A historical plaque on a stone wall details the construction of Cobb Hall, a defensive tower in the North East corner of the Balliol, which was built in the first half of the 19th century. It was originally a great deal of £500,000, but was later spent on £400,000 to strengthen the castle. The tower was constructed with three stories, two floors, and two hundred ten-inch diameter stone balls for the roof, and was designed to protect the North and East corners of the Balliol.