The position of this castle--as the penitents proudly styled their tower --was well-chosen, for from its summit they commanded not only the "short cut" to the oasis, but also the narrow shell-strewn strip of desert which divided the western declivity of the Holy Mountain from the shore, the blue-green waters of the sea, and the distant chain of hills on the African coast. Whatever approached the tower, whether from afar or from the neighborhood, was at once espied by them, and the side of the rock which was turned to the roadway was so precipitous and smooth that it remained inaccessible even to the natives of the desert, who, with their naked feet and sinewy arms, could climb points which even the wild goat and the jackal made a circuit to avoid. It was more accessible from the other side, and in order to secure that, a very strong wall had been built, which enclosed the level on which the castle stood in the form of a horseshoe, of which the ends abutted on the declivity of the short road. This structure was so roughly and inartistically heaped together that it looked as if formed by nature rather than by the hand of man. The rough and unfinished appearance of this wall-like heap of stones was heightened by the quantity of large and small pieces of granite which were piled on the top of it, and which had been collected by the anchorites, in case of an incursion, to roll and hurl down on the invading robbers. A cistern had been dug out of the rocky soil of the plateau which the wall enclosed, and care was taken to keep it constantly filled with water. Such precautions were absolutely necessary, for the anchorites were threatened with dangers from two sides. First from the Ishmaelite hordes of Saracens who fell upon them from the east, and secondly from the Blemmyes, the wild inhabitants of the desert country which borders the fertile lands of Egypt and Nubia, and particularly of the barren highlands that part the Red Sea from the Nile valley; they crossed the sea in light skiffs, and then poured over the mountain like a swarm of locusts.