《宋史·列传·卷八十三》
雄州北面过去因为打仗挖了很多陷马坑，城上则修楼，用以观察敌情，可以看到十里以内的情况；自从战争停止后，人们都不敢登城楼。
州北旧多设陷马坑，城上起楼为斥堠，望十里；自罢兵，人莫敢登。
In the past, to the north of 雄州, there were many pitfalls due to the wars, and buildings on the city wall were used to observe the enemy’s situation for a distance of more than ten miles; since the war ended, people dare not go to the tower.