Explore The Great Plains Missouri Oklahoma Kansas Nebraska Iowa South Dakota North Dakota Share The spectacularly eroded layers of sand, silt, ash, mud and gravel on display in BADLANDS NATIONAL PARK were created more than 35 million years ago, when there was an ancient saltwater sea here. The sea subsequently dried up; over the last few million years, erosion has slowly eaten away at the terrain revealing mesmerizing gradations of earth tones and pastel colours. The crumbly earth is carved into all manner of shapes: pinnacles, precipices, pyramids, knobs, cones, ridges, gorges – or, if you’re feeling poetic, lunar sandcastles and cathedrals. The rainbow hues that colour these formations are most striking at dawn, dusk and just after rainfall (heaviest in May and June). Among the best of the park’s marked hiking trails is the Door Trail, a less than one mile excursion from the large car park about two miles north of the Ben Reifel Visitor Center, which enters the eerie wasteland through a natural “doorway” in the rock pinnacles. A longer hike along the gently undulating Castle Trail, which winds through buttes and grassy prairies for ten miles (return), begins from the same parking area. Remember to carry more than enough water (particularly if you venture into the backcountry), as none is available beyond developed areas. The park is most accessible via I-90, which skirts the northern edge; a paved forty-mile road (Hwy-240, between exits 110 and 131) through the park is peppered with scenic overlooks.