Between each pair of milecastles lay two towers.The stone wall was to be 15 Roman feet high and 10 Roman feet wide.
在每对 milecastles 之间有两座塔楼。 石墙高 15 罗马英尺, 宽 10 罗马英尺。
英语百科
Milecastle
A milecastle was a small fort (fortlet), a rectangular fortification built during the period of the Roman Empire. They were placed at intervals of approximately one Roman mile along several major frontiers, for example Hadrian's Wall in Great Britain (Britannia in the Roman period), hence the name.