Speaking of large projects; they also destroyed the Walls of Benin and effectively erased mighty African empires from history.
> But the way Benin treated its slaves and the public display of large quantities of human remains hardened British attitudes towards Benin's rulers. Since 1863, the British had been trying to force the King to stop selling slaves to the Arab traders who had replaced the Portuguese after 1836 and to stop the practice of human sacrificial crucifixion.
Kinda off topic but the empire of Mali for example were claimed to have traded with people in south america before columbus set sail. Some documents claim that the king of spain instructed columbus on his second or 3rd voyage to find land south of where he originally landed, based on documents from the empire of Mali.
And sure enough he found south america.
But I'm sure the Malinese were also heavily involved in the slave trade.