The siting of the Ming dynasty imperial tombs was carefully chosen according to Feng Shui (geomancy) principles. According to these, bad spirits and evil winds descending from the North must be deflected; therefore, an arc-shaped valley area at the foot of the Jundu Mountains, north of Beijing, was selected. This 40 square kilometer area—enclosed by the mountains in a pristine, quiet valley full of dark earth, tranquil water and other necessities as per Feng Shui—would become the necropolis of the Ming dynasty.