What do you do when you've got a few hours to hang around a city and a bit of energy? Hire a bike. I did this when I was in Brisbane last weekend. Brisbane has the whole cycling thing well sorted including well defined cycling tracks.
It was enjoyable cycling along the river and across Brisneyland's bridges. Stopping near the swamps is not a good idea to talk on the phone. I was attacked by midges. Pesky little buggers! Today I'm so freakin' itchy!
The down side of hiring is that you may end up with a daggy helmet... Not a sleek as I'm used to.