Since we had entered the second court, we understood better--or at least I did, for Rouletabille, every moment more deeply lost in his own thoughts, seemed neither to see nor to hear--the topographical plan of the Fort of Hercules. As this plan is of the greatest importance in the proper understanding of the incredible events which were to occur so soon after our arrival at Rochers Rouges, I shall place at once before the eyes of the reader the general scheme of the buildings as it was traced later by Rouletabille and myself. The castle had been built in 1140 by the Seigneurs of Mortola. In order to isolate it completely from the land, they had not hesitated to make an island of the peninsula by cutting away the narrow isthmus which connected it with the mainland. Upon the mainland itself, they had built a barricade in the form of a semicircular fortification, designed to protect the approaches to the drawbridge and the two entrance towers. Not a trace of this fortification was left. And the isthmus, in the course of the centuries, had again resumed its old form, the drawbridge had been thrown down and the trenches had filled up. The walls of the Château of Hercules followed the outline of the peninsula, which was that of an irregular hexagon. The walls were built upon the rocks, and the latter, in some places, extended over the waters in such a manner that a little ship might have taken shelter beneath them, fearing no enemy, while it was protected by this natural ceiling. This design of building was marvellously well adapted for defense, and gave the inmates of the fortress little reason to fear an attack, no matter from what quarter it might come.