How to download TripleA maps?
Just after starting TripleA, click "Download Maps" button and copy the following link below and paste it into the text field:
Then click "List Games". And now you can browse and install various game types and maps.
A couple of them are particularly recommended:
World War II
World At War
The Rising Sun
World War II Revised
World War II v3
World War II v4
Twilight Imperium (twilight-imperium)
Red Sun Over China (Red_Sun_Over_China)
Battle of Aventurica
After choosing the desired map, buttons "Install Game" and then "Choose Game..." in the main menu screen are all that separate you from trying out these (and many others) maps. ;-)