Wall

The Wooden and Stone Wall allows you to place walls along the six edges of a Building's tile to increase it's defense. They are built automatically and do not need to be assigned Workers.

Stone Walls are superior, because they require special siege Cards to be damaged or moved over by your opponent, as opposed to Wooden Walls, which can be damaged by Units using melee attacks without requiring dedicated siege cards.

Buildings
Resources	Forestry <> Quarry <> Iron Mine <> Silver Mine <> Farm <> Pasture <> Windmill <> Fence <> Shed
Town	Town Center <> Watchtower <> Church <> Smith <> Dwellings <> Inn <> Bathhouse <> Town Guard <> Marketplace <> Harbor <> Wall (Wooden Wall, Stone Wall)
Castle	Castle (Wooden Castle, Stone Castle) <> Chapel <> Courtyard <> Stables