 The Arbuckle Mountains are the defining geographical entity in this region, with peaks (once taller than the Rockies) eroded down to their current elevation of 200-300' above the surrounding terrain.Many lakes are also located throughout the region, often shaped by the irregular topography of the underlying Arbuckle range.Larger manmade lakes include Lake Texoma, with over , and Lake Murray, a lake impounded about south of Ardmore.