Chapter 2 – Ancient Engineering
Great Zimbabwe in Africa – 1100-1500 CE
The Great Zimbabwe National Monument is a UNESCO heritage site.
The ruins of Great Zimbabwe – the capital of the Queen of Sheba, according to an age-old legend – are a unique testimony to the Bantu civilization of the Shona between the 11th and 15th centuries. The city, which covers an area of nearly 80 ha, was an important trading centre and was renowned from the Middle Ages onwards.
http://whc.unesco.org/en/list/364
Here is a good article by the well respected Guardian newspaper from 2016 exploring the engineering of this African city and the changing attitudes around who might have built it.
Designated a Unesco World Heritage Site in 1986, the preservation of Great Zimbabwe – led by the National Museums and Monuments of Zimbabwe organisation – is now challenged by uncontrolled growth of vegetation, which threatens the stability of its dry stone walls. The spread of lantana, an invasive flowering shrub introduced to Zimbabwe in the early 20th century, has put added of strain on the preservation work.