I've now Settled my 4th city.
I've also noticed that DZ has either scouts or Warriors all around me. He's had one fortified around my second city for a while, that has moved north to the new city. There's also a warrior by the copper in the S and another Scout by my capitol.
I don't know if he has iron working yet and can see where my Iron is, or is just keeping a close eye on me inpreparation generally. But as I don't need Iron to build my Gallic Warriors I think I will avoid conneting it to keep him guessing and keep my GWs out of sight.