How it began
Engaruka, in the Arusha region of northern Tanzania, was the home of an Iron Age farming community believed to have been established in the 15th century; one study places occupation from the 14th century. Researchers have confirmed that it once held seven villages with thousands of residents. Who the founders were is not known. The residents were most likely forebears of today's Iraqw people, who still use similarly intricate irrigation techniques.
How it works
Canals lined with stone blocks carried water from the Rift escarpment to stone-lined cultivation terraces. The system supported about 20 square kilometers of farmland. The site also has more than 1,000 hectares of sediment traps built to catch alluvial soil, and some fields were flooded to create paddy-like soils. Farmers kept cattle in stalls and used the manure to raise fertility and limit soil degradation.
Who pushed back
Engaruka was abandoned around the middle of the 18th century, for reasons that remain uncertain. Reduced river flow and territorial disputes with other ethnic groups are the explanations most often suggested. Other questions also remain unanswered, including how the community developed its farming system.
Where it stands today
The German traveler Gustav Fischer recorded the ruins in 1883 and compared them to the crumbled walls of ancient castles. Researchers describe Engaruka as the largest abandoned irrigated and terraced landscape in East Africa. A study published in The Geographical Journal in 2010 examined the physical and social factors behind its development.
