The size of the tombs of ancient Chinese emperors is often directly related to the size of the emperor's work before his death, and the larger the scale of the emperor's death, the larger the scale of the mausoleum. For example, the largest Han Dynasty imperial mausoleum is the Mao Mausoleum of Emperor Wu of the Han Dynasty, and the largest of the Ming Tombs is the Changling Tomb of Ming Chengzu.
Curiously, the largest and most imposing emperor mausoleum of the Tang Dynasty was not the mausoleum of Tang Taizong, Tang Gaozong, Wu Zetian, and Tang Xuanzong, but the tomb of Tang Ruizong. Tang Ruizong's exploits were not at the forefront of the Tang Dynasty, so why was Tang Ruizong's bridge tomb the most magnificent imperial tomb of the Tang Dynasty?
Emperor Ruizong of Tang was the younger son of Emperor Gaozong and Wu Zetian of Tang, and the father of Emperor Xuanzong of Tang, Li Longji. Li Dan's personality and ability were not suitable for being an emperor, but in the ever-changing political environment, Li Dan ascended the throne twice, which also led to Li Dan' emperor being basically manipulated and suspended.
In the first year of the First Heaven (712), Li Dan ceded the throne to Li Longji and retired to the position of Emperor Taishang, who held the highest power. In the second year of The First Heaven (713), Li Longji launched a "Congenital Coup" to regain imperial power, and Li Dan, who had lost his supreme power, lived in complete seclusion until his death due to illness in the fourth year of the New Century (716).
When Tang Ruizong Li Dan died, it was the time of kaiyuan's prosperity, and Tang Xuanzong used a lot of manpower and material resources to build a mausoleum for his father in order to fulfill his filial piety. Because of this, the scale of Tang Ruizong Li Dan's bridge mausoleum is extremely grand, and the scale layout and carving skills of the entire mausoleum fully reflect the atmosphere of the Tang Dynasty.
If Tang Xuanzong Li Longji had started and ended well, his mausoleum would certainly have been more grand than his father's. However, in his later years, Tang Xuanzong broke out a tragic "Anshi Rebellion", Tang fell from the peak of the prosperous world to a low point, and Tang Xuanzong was also usurped by his son because of the "Anshi Rebellion".
By the time Tang Xuanzong died, the Tang Dynasty had no conditions to build a large-scale mausoleum for Tang Xuanzong. As a result, Tang Ruizong Li Dan's bridge mausoleum became the only imperial mausoleum built in the Sheng Tang Dynasty, and naturally became the largest imperial mausoleum in the Tang Dynasty.