[In Chapter 11, Beholding the Stupa of Treasures,] the vast worlds surrounding our World of Endurance are purified three times. By placing the World of Endurance (Saha-world) in the center of those purified worlds, the Sutra shows us that the Buddhist ideal of a pure world must be realized here in our real world, and not somewhere else beyond reality.
Introduction to the Lotus Sutra