The Wheel of Reincarnation is the location in which spirits enter to be reincarnated.
The Wheel of Reincarnation is a large red wheel with golden spokes and reinforcement sections.
It always floats in the colorful sky of the otherworld, welcoming any spirits to be reincarnated. It can reincarnate still living beings and Shinigamis as well, if they end up entering in itself.
Once every few years, a cleaning day is held, where young Shinigami and their black cats come together to scrub the massive wheel, and the Shirushigamis are responsible for supervising the work.
Two members of Rinne's family ended up entering the Wheel of Reincarnation: his grandfather and his mother. And his father also almost got sucked into it, when his grandmother angrily kicked him for causing the wheel to be scratched, and Rinne himself while fighting Shirushigami Kain.