From Webkinz Insider Wiki
Most of Webkinz World is in Kinzville. For a long time members wondered what Kinzville looked like. Little glimpses of it were seen in places like the Kinzville Times Newspaper and the Adoption Agency but nobody knew exactly what it looked like. This changed when the Map of Kinzville was added to Webkinz World. Members were finally able to see what Kinzville looked like.
In response to a question about what lay outside of the boundaries of Webkinz World, the Creative Director once said: "We decided not to define Webkinz World beyond Kinzville. It was a small town where you got to go and meet fun characters and take care of your pet, and well, that was all we had to say. The rest was up to you."
One of the Trading Cards has sketch of Kinzville on it.