Just a few hundred meters from the Circular Mound Altar, you’ll see a group of buildings dating to 1530, built on the orders of Emperor Jiajing, which housed the Tablets of the Gods, sacred objects used for the Heaven Worship Ceremony.
The main building is the Imperial Vault of Heaven, a circular, red wooden pavilion with a blue double-pitched roof topped with a gilded sphere. All the buildings in the temple are covered with blue tiles, a reference to the color of the sky.
This building is 19 meters tall and has a diameter of 16 meters. As you can see, it rests on a two-meter-high, round marble base resembling an altar.
In the delightful interior, pink columns support the marvelous coffered roof, decorated with a bluish-green design featuring a golden dragon playing with a pearl, in the center, surrounded by another 360 smaller dragons, representing a round angle. On the altar in the center of the room, in the shape of a stone throne, is the Heavenly Great Tablet.
The two side pavilions, also in wood, were used to house the memorial tablets of the Gods of the Moon, the Stars, the Clouds, the Rain and Thunder and Lightning.
The complex is surrounded by the 193-meter-long Echo Wall. As you can see, it is flat and smooth, which allows soundwaves to bounce off it. If two people stand next to the wall, behind the two different pavilions, and whisper, they can hear one another.
An interesting fact: the study of sound waves was highly advanced in China, and this place is proof of that. The 18th marble stone as you move away from the entrance to the platform is the Dialogue Stone. If you stand there and speak, you can be heard by someone standing at the two far corners of the pavilion, 36 meters away; these three points form an equilateral triangle.
On your way out of the gate of the temple, if you stop at the first stone, facing the temple, and shout, you’ll hear an echo; if you move on to the second stone, you’ll hear two echoes, and three from the third stone.
