This tactic is only usefull if you are under a count attack and have no way to defend yourself.

However you can make it a nearly worthless settlement for the attacker.

What should you do ?

1. Research tear down buildings at the alchemist

2. Destroy your resource production levels 

3. If you still have time left destroy other expensive buildings or heavy needed buildings, this could be lvl 5 alchemist, residence

4. Finally start destroying the miller, if the conquered town has no free settlers it will become a slow process for the attacker to rebuild the town.

This tactic is only to be used when you don’t see any other way to defend your town. The attacker will be extremly annoyed that he took a town that is worth barely anything as most attackers go for the production levels.