The highest natural point in Pennsylvania rises 3213 feet above sea level. The rock-strewn plateau below has seen little habitation; apart from occasional frontier hunters or explorers and the traces of lumberjacks, geologists, and miners, people largely passed the mountain by. Inaccessibility, poor soil, and foul weather kept settlers on the slopes and in the valleys, so the plateau remained relatively undeveloped. To the northwest, just beyond the edge of the circular roadway, sorted stone patterns are visible, formed over many years as frost upheavals moved boulders into these arrangements. Hills to the north and southwest may seem higher than the high point, but this is an optical illusion: the northern point is 3192 feet above sea level, 21 feet lower, and the southwestern point is 3160 feet above sea level, 53 feet lower. Because the rounded hilltops are seen with open space beyond them rather than a background that gives the eye a point of relation, the senses can wrongly judge them to be higher.