The Mobile Suit Coliseum is located in Australia. It is a very good place to test the power of your units. If you win, each league gives you a good part or weapon as a reward. When outside the main office where the shops are located, run to the very back then run towards the screen. There is a secret room in the back of the coliseum filled with good items. If you manage to unlock the secret fight, it is the Organizer standing in between the two desks. He will pilot Burning Gundam and can only be hurt by melee attacks. He is difficult, but if defeated he will give you the Burning Gundam.