Use wall-in, it's SO good. Right, this is really simple... use farms/towers/barraks/mage towers etc. (anything that trains fighting units - best with buildings that train land units, so no gryphon aviaries or dragon roosts, thank you very much)
Just surround your town in them.
2.Foundry hide 'n' Seek
Well, your Foundry has less hit points than your Shipyard, AND without the Foundry, no more battleships or transports. And if you have any sense in that brain of yours you'd have more than one shipyard. Ok, here goes.