According to the ancient texts the original model for the Wheel of life was painted over the gateway of the Veluvana Bihara at Rajagriha on the instructions of the Buddha himself, who indicated exactly how the work should be done. The Buddha, was inspired by the activities of one of his chief disciples, Maudgalyayana . Thanks to his mastery of psychic powers, Maudgalyayana was able to visit all beings in the different realms of existence, and to see them in different states of pain or pleasure; as a result, he became aware of the causes of these different states .The Buddha realized that there were not enough people like Maudgalyayana to teach all those who needed to hear his teaching .He therefore instructed his disciples to paint the Wheel of Life ,a depiction of the different realms of existence , and their underlying processes ,at the entrance to every monastery .The picture is not strictly a literal account of worldly existence ,but is effective in that it appeals to our imagination with its rich and powerful imagery.
The wheel of existence is considered an endless life circle of human being. In the painting we can see a pig, a snake and a cock in the centre circle symbolizing ignorance, anger and greed respectively .These are the three cardinal sins of life which cause aversions and hindrances. The second circle shows good people moving upwards to heaven and the sinners being dragged down to hell. The third circle shows the six world of existence and the fourth and last circle shows the chain of cause and effect.The wheel of life is held by the lord of death or Yama which symbolizes that death is inevitable and good deeds or good karma lead to a better after life.