There is a sea cave below the escarpment of the easternmost mound that cuts clean through. Although there is a footpath through the cave, it is so pitch black that you can't see your fingers in front of your face; fortunately there is quite a clear light at the end of the tunnel.
東丘崖壁下有一個貫穿的海蝕洞穴，洞裡雖鋪設步道，但是一片漆黑，伸手不見五指，惟見洞口有光。