Introduction to the Bagua caisson: The caisson of Tianhou Temple is divided into two floors. There are two octagonal pillars on each side of the bottom floor. Each pillar is four buckets high. It is composed of 24 groups of brackets, which are assembled inward in a Bagua shape. , there are figures and hanging tubes of the Eight Immortals on each side of the caisson on this level. Above the figures of the Eight Immortals are Maoshu Ailian, Xizhi Aige, Yuanming Aiju, Hejing Yongmei, fisher, woodcutter, plowing and reading. The inner layer of the caisson is built with sixteen sets of Dougong, one on each side of the octagon, and two more Dougongs rise from each dome to gather in the top center, and a lotus is carved on the top mirror. The entire caisson looks like a web made by a spider, so the craftsmen also call it "spider's web".