Supporting Fortresses: Mutianyu Great Wall has both inner and outer supporting fortresses

Supporting Fortresses: Mutianyu Great Wall has both inner and outer supporting fortresses. Supporting fortresses are built outside the main wall according to the needs of warfare, following the mountain terrain and branching out from the main wall. The outer supporting fortress of Mutianyu is located on the outer side of the main wall, connected to the wall of Mutianyu No.11 Watchtower. The inner supporting fortress refers to the wall that extends southward from Dajiaolou, known as the "Bald-Tailed Border."