Sungbo's Eredo is Africa's largest construction, a 160km/99mi-long, 1050-year-old, 20m/65ft-high linear boundary rampart that once surrounded the ancient kingdom of Ijebu.

Read more about it here:

http://csweb.bournemouth.ac.uk/africanlegacy/sungbo_eredo.htm
http://www.newscientist.com/article/mg16322035.100-the-african-queen.html
http://www.nigeriansinamerica.com/articles/1735/1/Lunch-At-The-Sungbo-Eredo/Page1.html
http://query.nytimes.com/gst/fullpage.html?res=9C07EFD8113CF933A1575AC0A96F958260

This thread needs a bump.

I'll add more:

http://en.wikipedia.org/wiki/Walls_of_Benin

"Description

The walls are built of a ditch and dike structure; the ditch dug to form an inner moat with the excavated earth used to form the exterior rampart.
The Benin Walls were ravaged by the British in 1897. Scattered pieces of the walls remain in Edo, with material being used by the locals for building purposes. The walls continue to be torn down for real estate developments.[3][4]
The Walls of Benin City is the world's largest man-made structure.[5] Fred Pearce wrote in New Scientist:
"They extend for some 16,000 kilometres in all, in a mosaic of more than 500 interconnected settlement boundaries. They cover 6500 square kilometres and were all dug by the Edo people. In all, they are four times longer than the Great Wall of China, and consumed a hundred times more material than the Great Pyramid of Cheops. They took an estimated 150 million hours of digging to construct, and are perhaps the largest single archaeological phenomenon on the planet.[6]"

It is our history is destroyed. Torn down for real estate development.