Also known as the Upper Galleries, the last stop on the potted tour of the upper Rock is this network of tunnels - 4,000 feet of them dug out of the limestone by the British to defend against Spain and France´s siege of the colony in 1779-83, then during World War II, vastly expanded to some 34 miles worth. The stretch open to visitors, however, amounts to just 984 feet, with galleries branching off the main tunnel containing a few historical displays, mannequins, and so forth.