This is one of three tiers of marble guardrails defining the Circular Mound Altar. The balusters are intricately carved. Below them are dragon-shaped water spouts. At the winter solstice, a grand procession from the Forbidden City would escort the emperor to nearby Abstinence Hall. After three days of fasting, he would emerge at 4:00 a.m. and walk up the eighteen stairs of the Circular Mound Altar to the “celestial” center called the Heart of Heaven or Supreme Yang. Standing on the Tianxin Stone, he would conduct an ancestral, nine-phase ritual including a request for absolution, animal sacrifice and prayer for a successful new year. Circular Mound Altar (also called Terrace of Worshiping Heaven) was originally built in 1530. Then Yuanqiu was embellished with marble in 1749 on the orders of Qianlong Emperor, the sixth in the Qing Dynasty and China’s longest serving ruler.