Resembling a tidy lumber pile created by giants, these 60-foot basalt columns are a unique sight to behold. The formation of this National Historic Monument began when lava erupted in the valley a little less than 100,000 years ago and filled the area to a depth of 400 feet. Then about 10,000 years ago, glaciers overrode the fractured mass of lava and quarried away one side of the postpile, exposing and polishing a sheer wall of columns and enhancing the appearance of the natural hexagonal structure.
For a bird's-eye view of Devils Postpile, take the short but steep trail to the top. Here you'll see not only a cross section of the posts, but the smoothing effect of ice-polished tops on the basalt columns. The monument is just a 2-mile hike from beautiful Rainbow Falls, a worthwhile trek.
A shuttle bus is required during the busy summer months and departs from the Mammoth Adventure Center and The Village at Mammoth. Roads are closed over the winter, so the park is accessible only on Nordic skis or snowshoes. Driving is allowed during other times of the year, but you'll want to arrive early as parking fills quickly.