These are one of the largest man made structures ever to be constructed by man before 1st century, in the same category as the Pyramids of Giza and the Great Wall of China.
Its visible on google maps. The wall continues to be eaten up by expanding developments. The wall should get protections o that it can form a good tourist attraction feature and a source of African history to the next generation.
They are made of adobe. It still is a scientific marvel on how an adobe wall, left to the vagaries of nature eg sun and rain for over 1000 years old, can still stand intact to date. The workmanship is also perfect.