It is surrounded by a mile - high
rampart of material that was ejected from the crater — enough
rock to bury the continental United States under a two - mile - deep layer.
Accessed by the Pont Marengo bridge, jutting out over the shimmering waters of the Canal du Midi, historically, Carcassonne was the first fortress to adopt a «hoardings» system of defence in times of siege, wooden structures were fitted to the upper reaches of the
ramparts so that the castle's defenders had extra protection whilst they could lean over the walls and drop
rocks, hot tar and other projectiles on the assailants below.