 The cave network is a Scheduled Ancient Monument.The network of caves was first excavated in the 1830s by the Rev E Stanley, finding fragments of stone tools along with numerous animal bones which had been laid down over a wide period, probably accumulated in the caves by water action.The 'Old Cave' passage is a remnant of a former underground course of the River Elwy, eroded through the limestone and then left behind by the continued downcutting of the gorge.