Castle Improvements

Your castle offers you the chance to increase many different facets of your military or income. By spending resources, you can increase different parts of your castle to boost bonuses in the areas you want. Every part of your castle has a maximum bonus, listed below.

Your investment is summed in points, where gems are worth 12 points, mercury worth 6 points, lumber, stone, iron worth 2 points, Coal and CC worth 1 point. You may not invest food or mana in your castle improvements.
[rating] = [max bonus] * ( 1 - exp( -[points] / ( 1000 * [total land] + 15000 ) ) ) * ( 1 + min(3[masonries] / [land] , 0.60

Part Max Bonus Improvement
Science 20% Extra resources are just what your alchemists need to increase their effectiveness. Using the resources you provide them, they will give you a bonus percentage to your CC income.
Keep 20% Increasing the size of your castle keep increases housing, and as such gives you a bonus percentage to your maximum population.
Towers 30% The towers are the mystical centre of your castle. Adding resources to the towers means added tower construction, and thus a bonus to your wizard power.
Forges 10% Forges help to make the weapons you attack your enemies with. Stronger weapons mean a stronger military presence, thus boosting your offensive military power.
Walls 10% The key to any good castle defense, tall, strong walls help keep out invaders and protect you and your troops from harm. Adding resources to your walls increases your defensive military power.
Irrigation 30% The farming community greatly appreciates all the resources you invest in making the lands fertile. Adding resources to irrigation increases your food production.