What is a caisson?

It is a unique practice of indoor ceiling in ancient temples in China. When the ancients lived in caves, they often made holes at the top of caves to receive light, ventilation and access. After the emergence of houses, this form remains. Its shape is like an open caisson, and the "well" is decorated with algae, so the "algae well" is generally made into an upward convex well shape with a square, polygonal or circular concave surface, and decorated with various flowers, algae, wells, carvings and paintings. Mostly used in palaces, temples, thrones and the most important parts above the Buddhist altar.