Nigeria - Benin Iya / Sungbo' s Eredo

A six thousand five hundred kilometres square cluster of community earthworks run for about sixteen thousand kilometers in the Benin rainforest zone. The core of this cluster consists of tightly packed small settlement enclosures with narrow cordons sanitaires (no-man's-lands), and date back to about the C8th A.D. On the periphery, the earthworks have larger, wider-spaced primary enclosures (including that of Benin itself), much broader cordons sanitaires and date up to about the C15th A.D. Further west, around Ijebu-Ode, a 15 metres deep, 150 kilometres earthwork, is apparently an extension of the same technique depicting a later stage of socio-political development in an adjacent culture.