Terrain Bonuses Grasslands 10% Plains 10% Desert 10% Floodplains 10% Tundra 10% Ocean 10% Sea 10% Coast 10% Fresh Water Lake 10% Marsh 20% River 25%* Forest 25% Jungles 25% Hills 50% Volcano 80% Mountains 100% Structural Bonuses Fortified Units +25% Fortress +50% Barricade +100% Town Walls +50% Civil Defense +50% City +50% Metro +100% * This bonus applies to the defender if attacked from the other side of a river. Cities with resisters do not give defensive bonuses.