The selection of Colditz Castle as a high-security prisoner-of-war camp reflected both its natural advantages as a fortress and its symbolic value as a demonstration of German power and efficiency. Built in the 11th century and extensively modified over the centuries, the castle presented formidable obstacles to any would-be escapers: walls that were in some places more than seven feet thick, a position that allowed guards to observe the surrounding countryside for miles in every direction, and a single access road that could be easily monitored and controlled. The German commandant and his staff believed they had created the ultimate prison, a place from which escape was not merely difficult but virtually impossible.