Each building can have upgrades.
These upgrades can go from regular cosmetic modifications to incresed rooms or some other bonuses.
Example - simple
Make a big stone house-
Upgrades - Kitchen/basement/storage area or any room for that matter - Bi...
There must be different cultures wich have specific bonuses.
For example some cultures may have a small speed bonus/dmg bonus a tiny one while at the sandy area of the map or similar those in the north have more while on other types of land-may requ...