It’s a long one but worth it.A rainbow over Rainbow Falls.Credit: Eddy Joaquim/Getty ImagesKey PointsFish Creek Trail is a nearly 12-mile hike near Mammoth Lakes that winds through the Ansel Adams and John Muir Wildernesses to Iva Bell Hot Springs.Along the route, hikers pass Rainbow Falls, Fish Creek, granite peaks, forested landscapes, and panoramic Sierra Nevada views before reaching the natural soaking pools.The strenuous trail is best compl…