Miyun County covers 2,229.45km² which is the largest in area among all counties/districts of Beijing. The largest manual artificial lake in North China, the Miyun Reservoir, is located in North China like a piece of jade surrounded by mountains. With the maximum water area of 188km2 and the maximum reservoir capacity of 4.375 billion m³, the reservoir has steadily maintained its water quality in line with national category II drinking water standard. Thanks to fifty years of water conservancy, Miyun has become a green land of clean water, air and soil.
Miyun is a national-level ecological county, one of the most leisure and habitable counties in the world and also one of the first National Ecological Civilization Construction Pilot Regions. It is also a well-known longevity village in Beijing with over 600 old people aged over 90.
Miyun enjoys both mountains and waters, characterized as “80% mountain, 10%water and 10% farmland". Its mountainous area and water conservancy area account for 4/5 and 3/4 respectively of the total territory. Mountains, waters, forest and the great wall offset each other as an organic whole. It is known as the "Great Scene of Beijing Mountain and Water, and Suburb Park of the Capital" by well-known tourist experts.
Miyun has an average relative moisture of 61%, average temperature of 10.8℃, annual precipitation of 665.3mm and average frost-free season of 176 days. Its prevailing wind direction of the year is northeasterly with an average wind speed of 2.4m/s. With forest coverage of 72.5%, the county reaches the first in ecological quality in the City.