This sweeping and rugged mixed-grass prairie of the High Plains is where the buffalo roam and roam and roam. You may see a herd somewhere on the 1,800 glorious acres that form the Big Basin Preserve, a National Natural Landmark. Look for Big Basin signs and enter the preserve on the east side of U.S. 283 by crossing a cattle guard. Follow a driveway 1 mile east and north to a scenic overlook of the basin, a massive sinkhole that is 1 mile in diameter and 100 feet deep. This geological feature was created thousands of years ago by underground salt and gypsum formations that naturally dissolved over time. Return to the main driveway and continue ¼ mile east to a fork. The fork's east road leads ¼ mile to the parking area above St. Jacob's Well. The south road leads ½ mile to a stone marker. Watch for ruts; they can be deep on these dirt roads.