Kim Quy is the name, which is related to the legend of the Gold Tortoise in Sword Restoring Lake (Hoan Kiem Lake). According to this legend, after helping the king with defeating the enemy, the tortoise floated over the water surface and ask for the sword back before coming to the South China sea. When he came to this part of land, he met many evils and ask for being stayed and defeat them. After he exterminated all the devils, he was exhausted and stayed in a cave and turned into rock.
That cave is called Kim Quy by local people in Halong Bay. The cave is located on Dam Nam islet, which is about 100m long. There are many stalactites and a water spring flowing all year round. The image of gold tortoise turned to rock is still there as the evidence for the legend of the old god in Hoan Kiem lake.