Introduction to Xuanwu Lake: Xuanwu Lake is located in the core scenic spot of Huangyi Mountain. It is named after the forest of basalt pillars left by the volcanic eruption eight million years ago on the shore. The basalt pillar forest can be called a volcanic wonder. It is hundreds of meters high and straight in shape. They are all hexahedral stone pillars, only about fifty centimeters thick. They are neatly arranged along the lake, like knives and axes chopping them. It is huge in scale and rare in the world. The stone wall is divided into three layers. On top of the forest of tall upright pillars, there lies a forest of small pillars only ten centimeters thick. The cross-section is very similar to a honeycomb. There is another group of rough upright pillars above the honeycomb. The three groups of basalt pillars are integrated into a forest. One body. It is said to be formed by the accumulation of three volcanic eruptions of different ages.