If we may generalise from the most perfect specimens of Phoenician town-walls that are still fairly traceable, as those of Eryx and Lixus,[652] we may lay it down, that such walls were usually flanked, at irregular intervals, by square or rectangular towers, which projected considerably beyond the line of the curtain.  The towers were of a more massive construction than the wall itself, especially in the lower portion, where vast blocks were common.  The wall was also broken at intervals by gates, some of which were posterns, either arched or covered in by flat stones,[653] while others were of larger dimensions, and were protected, on one side or on both, by bastions.  The sites of towns were commonly eminences, and the line of the walls followed the irregularities of the ground, crowning the slopes where they were steepest.  Sometimes, as at Carthage and Thapsus, where the wall had to be carried across a flat space, the wall of defence was doubled, or even tripled.  The restorations of Daux[654] contain, no doubt, a good deal that is fanciful; but they give, probably, a fair idea of the general character of the so-called “triple wall” of certain Phoenician cities.  The outer line, or {proteikhisma}, was little more than an earthwork, consisting of a ditch, with the earth from it thrown up inwards, crowned perhaps at top with a breastwork of masonry.  The second line was far more elaborate.  There was first a ditch deeper than the outer one, while behind this rose a perpendicular battlemented wall to the height, from the bottom of the ditch, of nearly forty feet.  In the thickness of the wall, which was not much less than the height, were chambers for magazines and cisterns, while along the top, behind the parapet, ran a platform, from which the defenders discharged their arrows and other missiles against the enemy.  Further back, at the distance of about thirty yards, came the main line of defence, which in general character resembled the second, but was loftier and stronger.  There was, first, a third ditch (or moat, if water could be introduced), and behind it a wall thirty-five feet thick and sixty feet high, pierced by two rows of embrasures from which arrows could be discharged, and having a triple platform for the defenders.  This wall was kept entirely clear of the houses of the town, and the different storeys could be reached by sloping ascents or internal staircases.  It was flanked at intervals by square towers, somewhat higher than the walls, which projected sufficiently for the defenders to enfilade the assailants when they approached the base of the curtain.