Authentic introduction: Climb up the steps from the "workable" corridor in the southeast corner of the East Second Courtyard to reach the Upper Courtyard. It is a stone-studded underground passage between the Second Courtyard of the East Garden and the Dudu Mansion, Erlaotaiye Mansion, Shangjiang Mansion, Chuanxinyuan, Xinnan Courtyard, South Dudu Mansion, Changgongyuan, Wenchang Temple and other courtyards; it differentiates the heights of these two groups. Buildings of several feet are integrated into one. "Xing Ke Tong" runs through the first floor, which means that everything can be done and everything will be successful.