Great Zimbabwe
In southern Africa, the Kingdom of Zimbabwe raised a capital of massive, mortarless stone walls — the largest ancient structures south of the Sahara — grown rich on gold it traded down the coast to Arab, Persian, and even Chinese merchants on the Indian Ocean. Its ruins were so impressive that later European colonizers refused to believe Africans had built them and invented myths of foreign origins. It stands as proof of a sophisticated, wealthy African state plugged into a vast Indian Ocean trade world centuries before Europe arrived.
The path or medium of exchange moves, and a place or power rises or declines because it sits on or off the new route.