They were consistently dug as limestone quarries and by the 18th century, the caving-in of some of these quarries posed safety threats, so the government ordered reinforcing of the existing quarries and dug new observation tunnels in order to monitor and map the whole place.
他们通常是被作为石灰石采石场的， 直到18世纪 因为一些采石场顶板坍塌造成了安全隐患 于是被政府强制要求加固剩下的采石场， 并且挖掘新的观测隧道 来监控并给这整个地方绘地图。