The Southern Watch Towers.
Two towers were positioned at the confluence of the South wall and the river Taff. According to Speed’s 1610 plan, which contains the only reference to them, they stood closely together either joined by a short section of wall with a parapet or were joined by a building. It was an unusual arrangement, considering that single towers were chosen elsewhere in Cardiff’s town defenses. Presumably, there was a specific reason for choosing the applied design. This may have had something to do with the closeness of the river and the curvature in this part of the town wall. As later events should prove, this southern tip of Cardiff’s town wall was its weakest spot. In the late 18th and early 19th centuries the whole of the St. Mary’s church enclave was eroded and swept away by the Taff. Another reason for choosing this particular tower arrangement may have had something to do with the notorious tide levels in the Bristol Channel and the floodwaters, which constantly gave cause for concern.