Jincheng City, located in north China's Shanxi Province, was historically known for its rich mineral resources, especially coal. However, in recent years, Jincheng has been progressively reducing reliance on coal through ecological management and transformational development. The former coal wasteland is now a park with a forest coverage rate exceeding 80 percent. Longmahu Park, now a leisure spot and summer retreat with an average temperature of 22 degrees Celsius, is significantly cooler than other parts of the province. From a coal wasteland to an ecological lake, it reflects the city's transition toward a sustainable future.