The wheel is divided into four parts: 1. The hub, 2. Inner circle (divided into two halves), 3. The body of the wheel divided by five spokes and 4. The rim. All are in the grip of the wrathful Yama, the lord of impermanence and death. The hub depicts three spiritual poisons in the form of three animals: (black) pig symbolizes delusion (moha) (green) Snake, aversion, hatred (dvesa) (red) cock, passion (raga). The hub is surrounded by an inner circle which is further has two segments, the proper right side, from top to bottom shows the sentient beings who have done good deeds ascending to the world of gods, while the left from bottom upwards depicts those who have indulged in evil deeds and thus descend into hell.
The inner circle is surrounded by another circle, the main body of the wheel which is divided into five segments by spokes. In every segment the presence of celestial Buddhas has been shown. The upper one is heaven in which Gods have been shown along with the Indra's palace. The longer portion of the heaven depicts Titans who were later on expelled from heaven because of their pride. They fight the gods for the fruits of the wish-giving tree whose roots are in their realm but fruits in the world of the gods. It is said that gods born from lotus blossoms enjoy heavenly delights. They are subject to the law of anityata, of birth, life, death and rebirth. They may live for millions of years in heaven, but when their merits are exhausted they have to come down.
The heaven is followed by the human world on proper left side. The human world is generally the depiction of birth, disease, old age and death, a king, a monk near a stupa, struggle for existence etc. Here the human world is represented by a scene of labour by sweat of the brow; men tilling a field are shown. A stupa has also been shown.
Below the human world is the zone of tortured ghosts (pretas), which depicts emaciated and pot-bellied beings whose insatiable greed in past births has given them tantalizing thirst and hunger. Below heaven on proper right side is the animal world. The animals (tiryag-yoni) live in a fearful world of uncontrolled instincts. The lowest realm is the hell (Naraka), presided by Yama, the king and judge of the dead.
The outer most circle, the rim of the wheel, is made of twelve segments or interdependent causes of rebirth, like blind woman, potter, monkey plucking fruit, two individual rowing a boat, empty house, man and woman in embrace, arrow piercing a man's eye, a drunken man, child being born, a sick and old man being carried by another individual on the back, etc.
The Wheel of Existence is generally painted near the main entrance of a temple to instruct those who come to worship.
The painting is in light grey complexion with gold and black linings. The elaborate bottom border is decorated with auspicious symbols.
A. Waddell, Buddhism and Lamaism of Tibet, Delhi, 1978 (reprint)
P.V. Bapat, 2500 Years of Buddhism, New Delhi, 1956.
This description by Dr. Shailendra Kumar Verma, Ph.D. His doctorate thesis being on the "Emergence and Evolution of the Buddha Image (from its inception to 8th century A.D)."