IMPROVE    [days]                               time: varies    priority: 3

The improve order, when executed inside the castle, uses workers and stone to raise the improvement level of a castle.

     level   stone   worker-days
     -----   -----   -----------
       1       50       1000
       2       60       1250
       3       70       1500
       4       80       1750
       5       90       2000
       6      100       2500

improve runs for the specified number of days, or until the next improvement level is reached, whichever comes first.

Castles start at defense 50. Each level of improvement grants 5 more defense points.

A castle's improvement level also determines how many provinces may be garrisoned to it:

     castle     provinces      rank
     ------     ---------      ----
       0           1-5         lord
       1           6-12        knight
       2          13-24        baron
       3          25-37        count
       4          38-50        earl
       5          51-63        marquess
       6           64+         duke
                  region       king

     (A region must have at least 15 provinces to have a king)