Imperial Sand Dunes in Glamis, California.
We took a drive on Sunday to visit the Desert Tower Museum on US-8. The Desert Tower Museum commemorates the completion of the original road over the mountain pass. Part of building the road was figuring out a way to cross the Imperial Sand Dunes given the constant shifting sands. The original road was a plank road. If you are interested, here is the full story: http://www.desertusa.com/sandhills/plankrd.html