Swamp
Swamps are another type of valley that will increase your production of food by a certain amount. They are not that popular for players to conquer however, as they usually give worse percentage increase of resource production compared to the lakes you can also conquer. All valleys increase your resource production apart from flats, which are valleys you can conquer and build new cities on.
The percentage the valley will increase your resource production can vary from just 3 % up to as much as 36%. Like I said before, this depends on the level of the valley, but it can also vary between valleys of the same level too. Number of troops and type of troops that defend each valley also differs, but generally higher level valleys have more and stronger troops.
Expert Guide to Age 2
To become sucessfull and really do well in Evony Age 2 I really think you should get the Advanced Evony Strategies E-Book. Filled with secret strategies and tips it is definitly worth the cost, cheaper than a holiday package even.
Get it here.

