We did an open top bus trip around the city - 2 x 1hrs covered by 2 different buses. There are 2 companies and they do the same routes and are the same price. Worthwhile especially if you don't want to walk too much. ...
Mainly go to the Sky Tower, for great views of the entire area. There's a few parks and lots of stores within walking distance of the port. Just down the road from the port there's good souvenir stores. This was the least favorite of our ports and seemed to be the most industrialized. ...