The Devils Postpile formation is a rare sight in the geologic world and ranks as one of the worlds finest examples of columnar basalt. Its columns tower 60 feet high and display an unusual symmetry. Another wonder is in store just downstream from the Postpile at Rainbow Falls, once called a gem unique and worthy of its name. When the sun is overhead, a bright rainbow highlights the spectacular falls. This park is only open in summer, and must be accessed by shuttle from Mammoth Mountain Inn. Leashed pets are allowed in the park, and are allowed on the shuttle at the driver's discretion. Leashes must be no longer than six feet. Pets are not allowed in the buildings. Shuttle travel time is about 45 minutes to Reds Meadow (past the Monument), but there are 10 stops along the way to get out and stretch or hike. Once at the Monument, there is a short 1/2 mile walk. The John Muir Trail crosses the monument, so for a longer hike, join up with nearby trails that are in the dog-friendly Inyo National Forest.