Corridor introduction: Passing through this courtyard is a corridor that runs from east to west. The corridor is 66 meters long and nearly 5 meters wide. It is paved with stone strips. This corridor connects the Sanduotang courtyard. It is divided into two parts, the north and the south. To the south of the corridor is the outer house, which are the accounting room, the kitchen, the study, the small stage, the main entrance, and the east gate. To the north of the corridor is the inner house, which is the main building of the Sanduotang courtyard. It is composed of three deep courtyards, parallel to the east and west, each independent and connected to each other.