Introduction to Santianmen: The high platform where Santianmen and Xuanwu Pavilion are located is Chongtai, which is 6.1 meters high, 23.07 meters long and 19.8 meters wide. It is accessed by 24 steps decorated with stone railings. Santianmen was rebuilt in the Qing Dynasty, with masonry structure and double eaves on the top of the mountain.