Yes, that's the idea. Research The Wheel and connect one of your secondary cities to the capital with a road (or harbor). And, the gold yield for road/harbor connections is independent of the level of gold generation in the two cities. The larger the populations of your capital and the connected city, the greater the gold yield from the connection.
In BNW, "trade routes" (with caravans and cargo ships) is an additional source of gold (but different computation from road/harbor city connections).