In the linked save game. The city "Dragon's Capital" has produced 2 caravans already. The first one you can find just above "Dragon's Industry". The second one you can find just below "Dragon's Forest" and then you can see that it's got two more in the queue.

For some reason Dragon's Capital is able to produce 4 caravans. Why? I can't figure out. It's only a level 1 city, I have only researched the first trading tech.

The only thing odd about that city is that the Gilden faction used to be there to the left of the bottom fertile land.

From what I understand, that city (Like all the rest of mine) should only be able to have 1 caravan.

Note: I am running Heavenfall's bugfix mod in this game - https://forums.elementalgame.com/395013 (No adjustments to caravans)