In north of the Round Hillock. The emperor dome house was where emperors used to place the Goods tablet when loorshipping the Heaven. There is a round enclosing wall which was known as Echo Wall round it with its position near to the north side of the wall. Besides, there are two square buildings in the east and west and on entrance in the south of the enclosing wall respectively.

The left picture shows the sound-reflecting wall.

If two men A and B stand separately behind the two square buildings, when A whispers near the wall surface to the north, B will hear it clearly. This is also caused by the reflection to sound.

The right picture shows one of the top of round construction.