Answer: The Buddha’s head is covered with 18 circles of coiled hair, with the 4^th, 9^th, and 18^th circles containing horizontal drainage channels. Additional drainage and ventilation features include: interconnected caves behind the ears, openings at both sides of the chest (not joined). Together these form a hidden internal system of drainage, moisture reduction, and ventilation, greatly reducing weathering and erosion.

Image: Tuchong