The whole town was surrounded by a lofty wall, the height of which, on the side which faced the mainland, was, we are told, a hundred and fifty feet.[419] Towards the south the foundations of the wall were laid in the sea, and may still be traced.[420] They consist of huge blocks of stone strengthened inside by a conglomerate of very hard cement. The wall runs out from the south-eastern corner of what was the original island, in a direction a little to the south of west, till it reaches the line of the western coast, when it turns at a sharp angle, and rejoins the island at its south-western extremity. At present sea is found for some distance to the north of the wall, and this fact has been thought to show that originally it was intended for a pier or quay, and the space within it for a harbour;[421] but the latest explorers are of opinion that the space was once filled up with masonry and rubbish, being an artificial addition to the island, over which, in the course of time, the sea has broken, and reasserted its rights.[422] Like Sidon, Tyre had two harbours, a northern and a southern. The northern, which was called the “Sidonian,” because it looked towards Sidon, was situated on the east of the main island, towards the northern end of it. On the west and south the land swept round it in a natural curve, effectually guarding two sides; while the remaining two were protected by art. On the north a double line of wall was carried out in a direction a little south of east for a distance of about three hundred yards, the space between the two lines being about a hundred feet. The northern line acted as a sort of breakwater, the southern as a pier. This last terminated towards the east on reaching a ridge of natural rock, and was there met by the eastern wall of the harbour, which ran out in a direction nearly due north for a distance of 250 yards, following the course of two reefs, which served as its foundation. Between the reefs was a space of about 140 feet, which was left open, but could be closed, if necessary, by a boom or chain, which was kept in readiness. The dimensions of this northern harbour are thought to have been about 370 yards from north to south, by about 230 from east to west,[423] or a little short of those which have been assigned to the northern harbour of Sidon. Concerning the southern harbour there is considerable difference of opinion. Some, as Kenrick and M. Bertou, place it due south of the island, and regard its boundary as the line of submarine wall which we have already described and regarded as constituting the southern wall of the town. Others locate it towards the south-east, and think that it is now entirely filled up. A canal connected the two ports, so that vessels could pass from the one to the other.