The Trade Post allowed players to transfer resources from one of their towns to another. In addition to resource, you could transfer military units to other towns. It became available during the Classical Age, and improving it increased the amount of resources gained through trade and the maximum number of Trade Agreements a player can have. It was replaced by the Customs house in the Renaissance Age.
When transferring resources between settlements, a 10% gold transfer payment is required based on the total sum of all resouces being sent, rounded down.
When transferring military units between settlements, the gold cost is equal to the army value of the selected units.