Fields of Mistria's mysterious earthquake caused much damage to the idyllic titular town, breaking its stone bridge and staircases, plus presumably even damaging an old mill. That's where you step in as an adventurer helping to restore the town, which also involves restoring the mill to its former glory in a story quest called The Mill Restoration Project. If you can get the mill going again, you'll also benefit from it as another place to make more products for your farm. However, you might first wonder where to find the mill in Fields of Mistria.