Introduction to Chaimen: After the Poetry and History Hall, there is the fourth level of building - Chaimen. Chaimen is the smallest among the several main buildings, covering an area of ​​only more than 20 square meters and is only three or four meters high. "Chai Gate" was originally the courtyard gate built by Du Fu when he built the thatched cottage. Because of its simplicity and low height, the poet gave it such a well-deserved name.