Imperial Vault of Heaven

The Imperial Vault of Heaven sits to the south of the Altar of Prayer for Good Harvests connected by the Danbi Bridge, and sits to the north of the Circular Mound Altar. Facing south, it has a circular wall with three colored glazed gates. Founded in 1530, the 9th year of the reign of Emperor Jiajing of the Ming Dynasty (1368 - 1644), it is the place for housing the Gods’ tablets to be used at the Ceremony of Worshipping Heaven. Its main building includes the Imperial Vault of Heaven, West Annex Halls and East Annex Halls. The most interesting features are the Echo Wall, Three Echo Stone and the Dialogue Stone.

The Imperial Vault of Heaven is a round pavilion with a double-eave roof sitting on a two-meter-tall white marble platform. If you look at it from far away, you will find that the vault is like a blue umbrella with gold head. Stone fences enclose the platform. 19 meters (62 feet) in height and 16 meters (52 feet) in diameter, the hall is a finely interlaced wooden structure with a blue tile roof crowned with a gilded sphere. It has a coffered ceiling with a bluish green design of a gilded coiling dragon playing with a pearl at the center, and another 360 small dragons around. In the middle of the hall stands a circular stone seat carved with patterns, on which the Heavenly Great Tablet is placed. Many imperial ancestral tablets sit on both sides.
 

Imperial Vault of Heaven

The West Annex Halls and the East Annex Halls were dedicated to the memorial tablets of the moon, star, cloud, rain, thunder and lightning gods.

Inside Roof of the Hall

Echo Wall

 The Echo Wall encloses the Imperial Vault of Heaven. Its perimeter is 193 meters (633 feet). The wall is flat and smooth, which allows sound waves passing smoothly. If you and your friend stand by the wall behind the East Annex Hall and the West Annex Hall respectively and you whisper a word, then your friend will hear clearly what you said. The phenomenon utilizes the theory of sound waves, resulting in a "mysterious atmosphere".
 Three Echo Stones refers to the three stones from north to south on the stone road outside the gate of the Imperial Vault of Heaven. If you speak facing the vault while standing on the first stone, you will hear one echo; standing on the second and then the third stone, you will hear two and three echoes respectively.
 Counting from the platform, the 18th stone is called the Dialogue Stone. Standing on the Dialogue Stone, you can have a dialogue with someone at the northeast corner of the East Annex Halls or the northwest corner of the West Annex Halls, which is about 36 meters (118 feet) away. Magically, these three points compose an equilateral triangle with side length is 36 meters (118 feet). If you leave these three points, there is no such effect.

Next: Altar of Prayer for Good Harvests