In Lake City, Colorado, you can rent ice axes and climb walls of shimmering blue ice—for free—at the city’s sprawling local park. The park is set against the wild backdrop of the San Juan Mountains, a range known for its serrated ridgelines, deep snow, and brittle frozen cascades. Ice climbing in these mountains is usually reserved for experts and pros. But at the Lake City Ice Park, ice climbing is accessible to beginners. Some of the walls tower up to 170 feet, and most can be toproped, making them much…