score:6
This was an era when nearly all trade was via rivers and the sea. Movement overland was so much slower and more problematic that it was generally only resorted to when there wasn't a good naval alternative.
The town was at the confluence of the Sashe and Limpopo. Such a spot would naturally control and access all trade upriver on both rivers. The fact that the town increased in size and power to the level it did (probably only about 5,000 people, but that's still a lot for that time and locale), is all the evidence we really need that this is what was going on.
So the watershed below shows roughly the area that their commerce had access to. They would have had control of nearly all the trade in the upriver (western) half of this area.
The exports they had access to that were of interest abroad were primarily ivory and gold. This would have been tied into the Indian Ocean trade routes of the era via the mouth of the Limpopo.
Here's a map showing the Indian Ocean trade routes of the era (just before, technically). That curling river at the bottom is the Limpopo.
You can see it would have been a bit of a hike up the coast to the Mwenemutapa trading port of Sofala. So any external trade probably (technically) went through there first.
Upvote:1
By the time that Mapungubwe was a trading centre, the silk routes between Europe, Arabia, India and China were long established. As the linked article notes, trade would have travelled by sea up the East African coast and would have then travelled by sea or overland into Arabia, India and beyond.
Upvote:3
There was a north-south trade route with a long history between Zanzibar and the Horn of Africa and beyond through Mombasa and Mogadishu.
Just guessing, but it would seem natural for the Zimbabwe area's trade to feed into the latter, likely through Tete (where the Swahili operated a trade outpost before the Portuguese arrived) and the Zambezi.
I've no idea if there also was inland trade with kingdoms and tribes in the Great Lakes areas, but given how the Zambezi flows towards Central Africa it would seem reasonably natural for trade to have occurred upstream as well.