A Romanesque gladiatorial arena complete with a delayed-spawn warthog, a spectators box for Caeser, awnings to keep your pretty face from burning in the sun, and several hidden goodies to give you an upper hand in combat. Hot dogs are $5. Have fun and enjoy!
Map
Bungie.net : Halo 3 File Details
Pictures

Overview of the arena

Crude but effective spectator box for Caeser

A chariot to some, angry lion to others
I have also created a game type for this map if you are interested. Best with 4 teams of 2. Try different starting and secondary weapons for even more fun and varied game play!
Special thanks to 'SCARFACE 0890' for reminding me that Caeser needs a box. And to 'GTA Ruler1' for providing such an easy target in testing the gametype.