In Risk Australia (,New Guinea and Indonesia) is a continent called "Australia".
You get additional troop bonus reinforcements at the beginning of each turn if you successfully hold a continent. (I just counted.) Europe has 6 boarders to Green land, Africa and Russia. You'd basically need landmines to defend this place properly. Australia might be bottled in, but on the other hand AUSTRALIA IS BOTTLED IN. One way in or out. Siam. It's also half the size. Which means it's easy to completely conquer in your first turn if you have a foothold and then easy to hold so that you get your reinforcement bonus unless someone chooses to stick 10 horses in Siam, but the reinforcement bonus is 2/5ths the size of Europe so why bother unless you're being a prick and talking smack... And really if you can't talk smack while playing Risk, what's the fucking point?
(I feel very Rimmer right now.)