|• Village Hall||Adds walls to a town|
|• Fort||Adds moat and primary arrow tower to a town. Increases production of creature dwellings by 50%.|
|• Citadel||Adds two secondary arrow towers, standard walls are strengthened to fortified walls. Increases production of creature dwellings by 100%.|
As stated in the manual, castles provide increased security for towns. Fort adds wall to town's defenses. The wall is impassable by enemy creatures (without flying), but has a a drawbridge for defending creatures to pass through, back and forth if needed. Fort is also prerequisite for all creature dwellings. Additionally, building a Fort to a town changes the town's appearance on the Adventure Map.
The upgrade to Fort is Citadel, which adds primary arrow tower to town's defenses, and also adds a moat in front of the wall. An exception to this are Tower towns, which do not have a moat but instead building a Citadel adds several Land Mines in front of the wall. One of the greatest advantages of the moat is, that ground units end their movement to it, and cannot move further until their next round (see additional features Moat page). Note that this also works for defending creatures trying to get across the moat. Additionally, Citadel increases the creature dwellings' growth by 50%.
The final defense structure is Castle, which adds two more (secondary) arrow towers and strengthens the wall. The two arrow towers have half the strength of the primary tower added by Citadel. Further, production of creature dwellings is increased by 100%.