People underrate the Great Wall too much.
Its not a wall, its a weapon.
Still didnt vote for it though
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Its gotten buffed in Gods and Kings. Let me tell you what I mean...
You can ignore teching artillery for so long and go bombers/infantry to kill anything in your path. Once your bombers capture a city, any units left in it can't run due to Great Wall and you can pick them off one by one. You can use Paratroopers to drop behind enemy lines to snatch a city without an issue as soon as its hp is low enough. You can use the great wall to win any war (its better on multiplayer though)