Imperial Dunes, also Algodones and Glamis Dunes are the largest mass of sand dunes in the state, roughly 45 mi long by 6 mi wide (72km by 10 km). Area contains Imperial Sand Dunes Recreation Area, a popular destination for ORV (off-road vehicle) enthusiasts who have access to roughly 40% of the southern area of the dunes. North Algodone Dunes Wilderness area protected by California Desert Protection Act (1994). Formed by windblown sands of ancient Lake Cahuilla. Imperial County, CA.