I am in Sydney and would recommend:
* The Harbour Bridge Walk as Adam said
* Catch the ferry to Manly
* Take in an outdoor movie on the green at North Sydney Cricket Ground
* Check out the animals at Taronga Park Zoo
* If you have time travel to the Blue Mountains (just over 1 hour from Sydney) Once there you can see Sydney spread out on the skyline and ride the steepest railway in the world!
Have a great trip!
