Devils Postpile National Monument.

Located in the Reds Meadow Valley of the Eastern Sierra, Devils Postpile National Monument centers on a striking 60-foot cliff of hexagonal basalt columns. Formed by cooling lava nearly 100,000 years ago and later sculpted by glaciers, the formation is one of the world's most symmetrical examples of columnar jointing. Visitors can hike directly to the base or stand atop the "postpile" to see a natural mosaic of polished stone. The monument serves as a compact gateway to the Ansel Adams Wilderness, with the popular 5-mile roundtrip trail leading to the 101-foot Rainbow Falls, where mist frequently creates prisms in the afternoon sun. Access is seasonal and typically requires a shuttle from Mammoth Mountain, keeping the atmosphere quiet and preserving its rugged, volcanic character.