This is a little schem from my arena, for super-spleef minigame.
- Has 10 floors high
- the last floor is over a lava pool
- 51x51x55 blocks
and this plugins:
http://wiki.ess3.net/wiki/Group_Manager (from essentials) or something like this, for the permissions system
http://dev.bukkit.org/bukkit-plugins/super-spleef/ (the main plugin)
if you have problems like the schem explode, make a region with world guard, and add the flags, creeper-explosion and other-explosion to deny