I created my first world called Cascadia. I couldn't put it on the Exchange because the upload would time out before it would finish so I have a link to a download site that you could download it from. Here is the link:
http://www.mediafire.com/?maxynynnnmj
Its a mountainous land with lots and towns on the shelf of snow peaked mountains. Check it out! I would love any feedback or suggestions on how to improve it! Put your feed back on this forum topic: http://forum.thesims3.com/jforum/posts/list/167491.page
