Trayastrimsa hosts the most consequential family visit in Buddhist narrative. Queen Maya died seven days after the Buddha's birth, and tradition holds she was reborn as a deva. In the seventh rains retreat after his awakening, the commentarial accounts say, the Buddha ascended to Trayastrimsa and spent the three months of the retreat teaching the Abhidhamma, the systematic higher doctrine, to the assembled gods with his mother chief among the listeners, discharging toward her the debt no infant can pay. Each day he descended briefly to gather alms and repeated the day's teaching in summary to Sariputta, a framing by which the tradition explains the Abhidhamma's transmission to the human lineage.
The retreat's end produced the scene that Buddhist art has never tired of: the descent at the city of Sankassa on a triple stairway made by the architect god Vishvakarma, the Buddha on the central stair of jewels, Brahma with his retinue on the right stair of gold, Sakka on the left stair of silver, the moment, the texts say, when gods and humans could see one another plainly. Sankassa became one of the eight great pilgrimage places, and the descent is commemorated in festivals across the Theravada world. For the cosmology, the story does quiet structural work: it shows the heaven of the thirty-three as reachable, teachable and ultimately outranked, a place the Buddha visits, instructs and leaves.