City of Rocks National Reserve, Idaho The City of Rocks is truly a geologic monument; it is formed by large sculptured rock columns (pinnacles) or boulders rising as high as 40 feet and separated by paths or lanes resembling city streets.
The City of Rocks marked progress west for the emigrants headed for California and, for their loaded wagons, a mountain passage over nearby Granite Pass. It is now a favorite spot for rock climbing.
Castle Rocks State Park, Idaho is near the City of rocks and is another area known for its challenging rock climbing routes.
