Beijing's enormous urban area produces Bortle 8–9 skies, and regional haze can further limit transparency. Relief comes from the mountains to the north and west: the area around the Great Wall and the higher terrain of Hebei reach Bortle 4 within a couple of hours, with darker skies in the more remote ranges. Spring and autumn bring the clearest conditions, while winter can be cold and clear when winds clear the air. At 39.9°N, Beijing has classic northern-hemisphere skies, and the Great Wall makes a dramatic foreground for night-sky photography.