Most visitors see only one strip of this 375sq-mi park, but it is the most dramatic. The 39mi Badlands Loop Road traverses the northern rim of the Badlands, where prairie grasslands give way to buttes and hoodoos. The road passes long blond grasses that shimmer in the wind like a shaken sheet, then straddles and dips down into the gullies. Wildflowers speckle narrow stream canyons, steep and barren or intricately carved slopes, high-ridged and tiny sodded buttes. Pinnacles Overlook is a sweeping viewpoint to the south. Formations are bleached white on top, then bleed pinkish to a tawny yellow. Tiny white flowers-Hood's phlox-bloom in the broad expanse of gray. The Castle Trail (4.5mi) is spectacular in early morning when the moonscape valley and pointed spires get their first dose of light. The Cliff Shelf Nature Trail (.5mi) is popular for its shady juniper trees. The boardwalk winds through a slump, a wet place in dry country, where water retention has created an oasis of green.Four units comprise Badlands National Park. Park headquarters are located at the Ben Reifel Visitor Center, at the east end of the park road. The North Unit, through which Badlands Loop Road runs, and the adjoining wilderness Sage Creek Unit are surrounded by Buffalo Gap National Grassland. The undeveloped Stronghold and Palmer Creek Units are within the Pine Ridge Indian Reservation, to the south; they are served by the White River Visitor Center