Also, ouch:
http://www.pcgamesn.com/article/how-big-war-zs-map
That's 116 squares, which gives us a total of 9.7417 square kilometres.
There are margins of error of course. The height of the character throws things out of whack considerably, but not enough to get even close to a 100 square kilometre result: if we'd assumed each character was seven feet tall that would give the map an area of around 14 square kilometres. If you count every square on the map, accessible or not, you'd still only get 21.5 square kilometres. If you assumed that walking pace was something much faster, say 6mph, the map size goes up to 35-40 square kilometres. Without a reliable standard it's difficult to come up with an exact result. But 100 square kilometres isn't it.
http://www.pcgamesn.com/article/how-big-war-zs-map