A story in the The Voltage on the Earthworks of Benin:
Benin city, located in the south-south of modern day Nigeria was enclosed by massive extensive walls in the height of her influence and strength. The Walls of Benin City is the world’s largest man-made structure. Fred Pearce wrote in New scientist, in his words:
“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 pyramids of cheops. The entire work of the Benin moat took about 150 million man hours of digging to achieve, the Benin moat can be arguably the most single largest archeological work in the planet” Pearce 113)”...[more]