The prayer wheels symbolise meditation, and tranquillity is the essence of meditation - to achieve a state of supreme serenity and quietude. A state of bliss that is about inner calm, so you take situations and events with patience, without being weighed down.
The prayer wheels fade over time, and it is this imperfection that makes it beautiful. It reflects the belief and faith which is the foundation of a tranquil state, of a purpose fulfilled – the glow of which is visible in the old lady with wrinkles as much as in the curiosity of the small boy touching the wheel. It is this purification, which is liberating and inspiring!