Grey Cloud Dunes Scientific and Natural Area -- Located near Cottage Grove, MN. Parking at the corner of Hadley Avenue and 103rd St., and at the end of 110th Street. It's a rare prairie with dunes rising in waves cresting 10 to 20 feet. Plants include little bluestem, penstemon, prairie dropseed, sand reed grass, gramma grass, and silky prairie clover plants. Tree species consist of elm, silver maple, cottonwood, and box elder.