Tibet is a high mountainous plateau with most of its land over 12,000 feet above sea level. The sky appears a very deep azure blue, and the sun blazes with a searing white intensity. The silver lining of the clouds may suddenly refract all the colours of the rainbow. Great skill is employed in the depiction of clouds in Tibetan Thangka paintings. The pure clarity of the sky is metaphorically an illustration of Buddha Mind. Clouds may come and go across the heavens, like the transitory thoughts or delusions which appear to obscure the mind's true nature, yet the nature of the sky remains unchanged. Like the mirror, which is always unaffected by the appearances which arise in it, the sky is clear, transparent, infinite, and immaculate.