Built in the ninth year of Emperor Jiajing’s reign (1530) in a round shape with a double-eaved roof, it was the main hall of the Vault of Heaven of the Circular Mound Altar, housing the Gods’ tablets to be used at the ceremony of worshipping Heaven. It was renamed the Imperial Vault of Heaven in the 17th year of Emperor Jiajing’s reign (1538) and rebuilt into the present style in the 17th year of Emperor Qianlong’s reign (1752).

With a height of 19.5 metres and a diameter of 15.6 metres, the hall is a finely interlaced wooden arch structure with a blue tile roof crowned with a gilded sphere, looking elegant and majestic. It has a caisson ceiling with a bluish-green design of a coiling gilded dragon playing with a pearl at the centre. It is indeed a masterpiece of ancient architecture in China.