CDB - The City Defence Bonus
As questions have resurfaced lately in regard to the CDB (City Defence Bonus) value, here's a quick reminder, or primer for newer players:
The CDB is displayed on the left-hand side of the toolbar top centre:
It shows a value which expresses which additional defensive bonus units defending the city outside the Acropolis will receive: 100 CDB points add 1% defence:
Defensive bonus in % = (CDB / 100) / 100
In the above screenshot, for example, this would add up to:
+141,69% = (14.169 / 100) / 100
An additional +150% defensive bonus is nothing to sneer at, though it will take some time and more than a few Drachmas to get there, but it can be done. Below you'll find a table with all fortifications, buildings, decor and other elements which are able to contribute to the CDB:
Note that the maximum total shown above can be improved with special city schemes and decor and that it does make a slight difference if one is playing on a plarium.com or Facebook server.
This forum thread also discusses city scheme bonuses and CDB values in general.