caravan cities?

Please let me know the meaning of the phrase “caravan cities”?

What is the context?

It is in the following sentence:

‘The agents of the wealthy Ka-rim families could be found in major ports throughout the Indian Ocean trading area, as well as the caravan cities of sub-Saharan Africa and the East African ports.’

A caravan city is probably similar to a trailer park.[YSaerTTEW443543]

TOEIC listening, photographs: A shipyard[YSaerTTEW443543]

I think it’s more likely a city that was founded on the trade of caravans, in the traditional sense of groups of travelling traders. See