Welcome to the Q&A Forum

Hi Louie, It seems unlikely to me (which doesn't mean it's impossible) that they have a city-specific penalty. Can't say I have ever heard of that before either, and I would say it would be hard for Google to decide on something like that, manually or algorithmically. The idea that it could be a large number of links from the Sydney region honestly seems like a stretch: that should really just result in a link-based penalty that affects the site nation-wide. Where this could have happened, however, is if someone abused directory links with way too many links using "sydney" in anchor text but I'm sure you'd have seen something like that already. Even then, I haven't heard of that hurting all rankings in that region alone, but rather just for queries including "sydney". Have you tested this searching from IPs in each region, i.e. I just wanted to make sure it's 100% confirmed that the site does rank well and receives traffic from Brisbane, Melbourne, Perth etc. and that you are not seeing personalised results in those locations and not in Sydney. I know it seems like grasping at straws but it's a really weird case for a non-geo-specific query.