Far north of the municipality in the Yanshan range are Yanqing and Miyun Counties, and Huairou and Pinggu Districts, both of which were rural counties until 2001. The far north is rugged, rural and sparsely populated. Yanqing, Huairou and Miyun all have fewer than 200 residents per km2 (518/sq. mi.). They are perhaps best known for stretches of the Great Wall, with Badaling and Shuiguan in Yanqing, Mutianyu, Huanghuacheng and Jiankou in Huairou, and Gubeikou and Simatai in Miyun, and Jiangjunguan in Pinggu.