Mike - aka Plane Walker, aka soulraven666 - over at NWN2 Mods has posted a step-by-step tutorial on creating a "roman Colosseum."
I thought I would detail the process I am going through in creating this Arena so this post is going to be an ongoing one that I continue to add to as I progress. Please feel free to reply with comments.
Head over to the NWN2 Mods forum and check it out:
http://www.nwn2mods.com/forums/index.php?showtopic=21