Southern? But the Wall is only in the North:
(here in red and yellow)
Its purpose was to protect the Empire from invasions from the North (Mongolia)
There is a Southern Great Wall, too. Much less known than its northern twin it was built during the Ming to protect against Miao tribes. It's located in Hunan Province, neighboring Guilin Province. It's going west though and I thought they'd be hitting east towards Tibet but that might come later then...