What is the shadow wall?

As soon as I entered the gate, I saw a wall, which is the shadow wall:

The back wall is the first wall that tourists see when they look up at the gate. Designers who pay attention to looking up and seeing happiness often use the shadow background wall to design auspicious patterns to achieve the purpose of beautification. In Wang Fu and the homes of some dignitaries in the city, many shadow walls are decorated with colored glazed tiles. What's more, tile fish pots are placed under the shadow walls, and ornamental lotus flowers are planted. koi fish and lotus flowers that reflect sunlight in the water are also quite exquisite.