The symbolic force of the octagonal shape is universal. The octagon is the source of all foundations in the history of civilizations. It is the central figure of the YI Jing (Book of Changes), developed in the beginning of the first millennium before the Christian era in China. The octagonal form is used to describe the states of the world and their evolution. It allows the principles of Yin and Yang: opposition-complementarity (sun and moon, white and black, etc.) and subdivides this duality in a systematic way. 

Since Antiquity, then in the Judeo-Christian era, as in Chinese symbolic thought, the circle symbolizes the sky, and the square represents the earth. In architectural art, these forms are omnipresent. The square is drawn inside the circle. The octagon is located between the square and the circle. It is the link between the material world and the spiritual world.