Mauna Kea's summit is one of the best sites in the world for astronomical observation due to favorable observing conditions. The arid conditions are important for submillimeter and infrared astronomy for this region of the electromagnetic spectrum. The summit is above the inversion layer, keeping most cloud cover below the summit and ensuring the air on the summit is dry, and free of atmospheric pollution. The summit atmosphere is exceptionally stable, lacking turbulence for some of the world's best astronomical seeing. The very dark skies resulting from Mauna Kea's distance from city lights are preserved by legislation that minimizes light pollution from the surrounding area; the darkness level allows the observation of faint astronomical objects. These factors historically made Mauna Kea an excellent spot for stargazing.