What are they good for? Absolutly nothing. Does anyone use them? Considering how carefully the other improvements were designed, I can't imagine why they deemed it necessary to attach the -1 food rider. If you have excess food you are probably better off with whipping, and if you had put cottages on there instead you'd have enough cash now to rush your productions. The only real reason I see to use them is to convert a city into a SS factory in the late game (since these cannot be rushed). Was the covering of terrian with mines considered exploitive in the previous Civs?