Perched atop Castle Rock, Stirling Castle possesses a large esplanade outside of its main gate. Originally meant to be an open area to allow the castle's defenders a view of those who approached, it also provided a clear field of fire in battle. In 1809, with the military situation in Scotland peaceful, the esplanade was redesigned as a parade ground. Much of the castle's outer defenses were constructed between 1708 and 1714 by Captain Thomas Dury. These consist of thick, low-set walls designed to resist artillery bombardment. Dury's work incorporated the castle's earlier outer defenses which were built for Queen Mary of Guise in the 1550s. These include part of the "French Spur" which provided flanking fire across the front of the outer wall. Within the outer defenses is a small pocket, Guardroom Square, which is dominated by a higher set in inner walls. The outer defenses were also protected by a deep ditch and drawbridge.