I've stumbled across this potential Unesco World Heritage site called Sungbo's Eredo, the person who showed it to me made some very intriguing claims, such as this was taller than any walls in ancient Rome and nearly as large as the Great Wall of China.
I've tried looking into it but there only seems to be a Wiki article on it making the same claims, with all of the sources for that page seeming quite dubious or non-existent. Also a number of online articles are making the same claims and touting it as an amazing undiscovered part of human history.
My question is, how much of this is true? Can anyone verify any of these claims? I'm not making any judgements, my gut is just telling me something is off here and every picture I've been able to find just looks like either basic earthworks or pictures of hillsides without any references which were posted on Afrocentrist blogsites like this: https://blackattraction.tumblr.com/post/31768734296/osun-osogbo-sacred-grove-osun-state
No and yes. The Sungbo's Eredo is not a largest 'piece of earthworks' created throughout history, as with its length of 160 km it is somewhat impressive, but is nothing to speak about in comparison to much more complex and usually larger structures erected in China or Europe, although it is possible for it to be a the largest continuous earthwork structure (contrary to the common name, the Great Wall of China or Walls of Benin are a network of fortifications rather than a single, continuous structure spanning thousands of miles). It is true, however, that southern Nigeria is a site of a possibly largest network of interconnected earthworks (iya), built in the area around Benin City, in the Edo State that lies eastwards from Ogun State, where Sungbo's Eredo is located. Although the collective length of the former is disputed, the upper estimates suggest length of 16.000 km (10.000 miles), making it definitely the longest known network of earthworks (or fortifications for that matter) anywhere in the world. Initially thought to be constructed somewhere between 13th and 15th centuries, archaeological examination has shown that the oldest parts of the network located near Ekhor n'Iro were erected around late 8th/early 9th century, what more or less corresponds to the time of Sungbo's Eredo construction.
Now, concerning the height of the walls is not that impressive. Fortifications in Ogun state were constructed as a ditch and rampart, i.e. with the earth dug up to create the ditch has been deposited on the inside of the latter's perimeter, forming an earthen wall. Even though the difference between a bottom of the ditch and crown of the wall might reach 20 meters or more, the wall is generally wider than the ditch resulting in the average height closer to 7-8 meters between the ground level and the crown of the wall. Thus, the statement that they were higher than the walls existing anywhere in Rome is misleading, as e.g. the Aurelian Walls expanded in 4th century CE reached 15 meters in some places.
So, although the claim about Sungbo's Eredo being taller than the walls in ancient Rome is incorrect, the earthworks are among the longest in the world (being possibly the longest continuous piece of earthen structure) and it neigbours a largest known network of earthworks around Benin City.
Darling, P., Nigerian Walls and Earthworks, in: Emeagwali, G., Shizha, E., (Eds.) African Indigenous Knowledge and the Sciences: Journeys into the Past and Present, Brill, Leiden 2016, pp. 137-144.