The canna of the town is 64 braccia and the canna of the wall is 16 braccia.

The tower of the citadel that is to be made between the ravelin of that citadel and the angle that looks toward the sea must be entirely solid, except for the lateral defenses and the interior of the parapet which is encircled by the upper part of the tower. And the talus which surrounds the said solid tower from below must rise up to 2/5 of the height of that tower, that is 8 braccia. And it must project as much beyond the foot of the tower. In which talus let there be made the defenses of the foot of the tower, and likewise of the other walls, together with the ditch. And between the said defenses and the foot of the tower let the road be interposed by which one goes to the said defenses, which shall be 4 braccia high and 4 wide, in which one may well handle every artillery fit for such defenses. And let each defense have its own flue, which gives outlet to the smoke along the solid of the tower. And let the mouths of such flues be wide where they touch the tower, and narrow on the part that faces the tower. And thus we shall have made a casemate joined to the foot of the tower, which with its defenses guards against the cutting-away of the tower at its foot, and against the cutting-away of itself, that might be attempted by any device of the enemy. And its defenses must begin level with the ground, so that the enemy cannot hide himself below the line of defense. And let the spaces set between the defenses be angled toward the bank of the ditch, so that the enemy may not make a shield of such intervals. And let a grated gate be left toward the sea, so that if the enemy should cast earth from the bank of the ditch to cover such a defense, our men may be so ready and apt to throw that earth into the sea as the enemy [throws it] into the ditch. And the defenders of such a place must have their entrance by the angle of the fortress, which joins with the tower by a stair which may be drawn up by the castellan, so that if, by mishap, the enemy should make himself master of it, he cannot pass any further. But with smokes and fires and other fetid things cast by that way, let him make the enemy clear out in fury.