Topped with rolls of barbed wire, it doubles up in places to form both an inner and an outer perimeter, with a strip of concrete in between for guards to patrol along.
Inside the secured perimeter were several inner circles of fencing as well as barriers on both sides of roads where in most cases Chinese militia were standing every ten paces.
The weight of the building is supported entirely by 12 stout outer columns, which form the square perimeter of the building, plus four inner columns at the corners of a smaller, inner square.