Every settlement has 1 available point of Development per 100 population, rounded up.
A holding costs as many Development Points as it has in ranks. eg. a rank 3 Temple costs 3 Development Points.
In order to rank up a holding, there must be at least two other holdings of similar size. eg. a rank 2 Temple that wants to go to a rank 3 Temple needs there to be two other rank 2 holdings in town, of any kind.
Kinds of Holdings :