The Mine is a structure which allows miners to obtain iron ore and coal. It cannot be removed from the landscape, but the upside is that it produces massive amounts if iron and coal. The downside is that while the player can remove the wooden or stone part of the structure, they leave a heap of dirt or a pit in the ground, and the land is wasted forever.
Coal can be used as an alternative fuel source to replace firewood. This can reduce the need for so much forest area, at the expense of having more miners. Coal can be used by the blacksmith to make steel tools which last longer than iron tools.
It needs to be placed on a hill or mountain and requires a large workforce.