cities destroyed by monsters should be "re-settle-able"

"Re-settle-able" likely isn't a word in English but in the world of Elemental it should be.  I had a forest drake wander into my territory from Resolin fairly early on (my sov and champ were probably around level 4 or 5) and obliterate 1 of my 3 cities.  

Maybe I should've built a warden closer to it so all my borders were covered.  Not sure if a warden would stop a forest drake.  Given that I was hemmed in by other empires, the loss of that city was game over for me since that was where I trained my troops.  My other 2 cities couldn't hope to match it's level of output.

Playing on normal, small map.