Sungbo ' s Eredo Sungbo ' s Eredo is a rampart or system of walls and ditches that is located to the south - west of the Yoruba town of Ijebu - Ode in Ogun state , southwest Nigeria ( ) . It was built in honour of the Ijebu noblewoman Oloye Bilikisu Sungbo , and is reputed to be the largest single pre - colonial monument in Africa . Description . Total length of fortifications is more than . Fortifications consist of a ditch with unusually smooth walls and bank in the inner side of ditch . The height difference between the bottom of the ditch and the upper rim of the bank on the inner side can reach . Works have been performed in laterite , a typical African soil consisting of clay and iron oxides . Ditch forms an uneven ring around the area of ancient Ijebu state , an area approximately wide in north - south , with the walls flanked by trees and other vegetation , turning the ditch into green tunnel . As a construction project , it required more earth to be moved than the Great Pyramid of Giza . History . The Eredo served a defensive purpose when it was built in 800 – 1000 AD , a period of political confrontation and consolidation in the southern Nigerian rainforest . It was likely to have been inspired by the same process that led to the construction of similar walls and ditches throughout western Nigeria , including earthworks around Ile - Ife , Ilesa , and the Benin Iya , a series of connected but separate earthworks in the neighboring Edo - speaking region . Sungbo ' s Eredo has also been connected with the legend of the Queen of Sheba which is recounted in both the Bible and Koran . In the Old Testament , she is described as having sent a caravan of gold , ivory and other goods from her kingdom to King Solomon . In the Koran she is an Ethiopia n sun worshiper named Bilqis involved in the incense trade who converts to Islam . Legends of the contemporary Ijebu clan link the Eredo to this fabled woman , a wealthy , childless widow who they know as Bilikisu Sungbo . According to them , the monument was built as her personal memorial . In addition to this , her grave is believed to be located in Oke - Eiri , a town in a Muslim area just north of the Eredo . Pilgrims of Christian , Muslim and traditional African religions annually trek to this holy site in tribute to her . It is believed that the Eredo was a means of unifying an area of diverse communities into a single kingdom . It seems that the builders of these fortifications deliberately tried to reach groundwater or clay to create a swampy bottom for the ditch . If this could be achieved in shallow depth , builders stopped , even if only at the depth of 1 meter . In some places small , conical idol statues had been placed on the bottom of the ditch . The impressive size and complex construction of the Eredo drew worldwide media attention in September 1999 when Dr Patrick Darling , a British archaeologist then with the University of Bournemouth , surveyed the site and began publicizing his bid to preserve the Eredo and bring the site some prominence . Previously , the Eredo had been little - known outside of the small community of residents and specialists in Yoruba history . Forty years passed between Professor Peter Lloyd ' s publication of his analysis of the site and that of Darling , but it still served to necessitate a complete rethinking of West Africa ' s past . World Heritage Status . This site was added to the UNESCO World Heritage Tentative List on November 1 , 1995 in the Cultural category .