Natural light pillars illuminate night sky in N China

Natural light beams illuminate the night sky in Hulunbuir City, north China's Inner Mongolia Autonomous Region on March 6 morning. Known as “light pillars”, they are a rare optical illusion caused by falling ice crystals that reflect sources of light on the ground. (Photo: China News Service/Wang Ying)

Natural light beams illuminate the night sky in Hulunbuir City, north China's Inner Mongolia Autonomous Region on March 6 morning. Known as “light pillars”, they are a rare optical illusion caused by falling ice crystals that reflect sources of light on the ground. (Photo: China News Service/Wang Ying)

Natural light beams illuminate the night sky in Hulunbuir City, north China's Inner Mongolia Autonomous Region on March 6 morning. Known as “light pillars”, they are a rare optical illusion caused by falling ice crystals that reflect sources of light on the ground. (Photo: China News Service/Wang Ying)