Sundog over city buildings. Colorful sundog (centre) against a blue sky, seen over silhouetted buildings. Clouds are seen across top. Sundogs, or parhelia, are luminous and sometimes colourful areas which appear on both sides of the sun at the same elevation in the sky (one one side seen here, Sun at left). They are caused by the refraction of sunlight in hexagonal ice crystals present in the atmosphere. Photographed in 2012, in Turku, Finland.