What to do in Sydney for FREE on day three :)

Oz has proven to be very expensive so I am making every effort to get back on budget through finding FREE things to do in Sydney… Unfortunately when I go to tourist information at the Rocks they confirm that I have already visited most of the free options on my hikes around the city 0_0 Good to know that I have a keen eye for freebies ;)
However, I had not yet visited the Observatory so a quick walk around the Rocks through the public art area and along, what must be, the narrowest alley to feature public art! Onto the oldest street in the settlement ‘George Street’ renamed after King George from the former High street, the most fascinating fact about this street is that it was once covered in wooden paving blocks (some of which remain) to make the ride more comfortable for carriages. Try and keep your eyes open for both hidden pieces of artwork and history boards which proliferate in this area of the city. Or, try coming up with your own piece of art - my ‘petal’d tarmac’ has that screensaver quality ;)
Walking uphill you will soon arrive at the Garrison Church directly below Observatory Hill and from here it is a quick walk to the Observatory itself with its nautical flags on full view fluttering in the breeze outside. The centre is open both day (for the exhibitions) and night (for star gazing / Astronomy) and is worth a visit if you are at a loose end - the building itself has wonderful copper roof details which have turned green over time while inside is a veritable treasure trove of all things astronomical. You will find a range of telescopes, star charts, planetariums, solar systems, working models (one of which whirls through a year for the Sun, Earth and Moon), videos and interactive exhibits. All in all enough to keep you entertained for at least 30mins or more… The Observatory hill also provides some of the best views of the Harbour Bridge…
Within the Rocks you will also find ‘The Rocks Discovery Museum’, which is also free and filled with archaeological artefacts many of which came from the YHA Big Dig site!! Housed within three old houses linked together you get a feel for the space a family with 8-10 children would have had 0_0 before climbing the creaking wooden steps to the first floor where you are greeted with ‘Hello Sailor’… before seeing the final exhibits on clothing (including the very miniscule corset and working boots) and a rat trap complete with desiccated rat!! Once again considering this exhibition is free there is plenty to see and several interactive exhibits - if you are interested in the history of the area this is the place to come after the YHA Big Dig site.
Complete list of Free things to do in Sydney:
Rocks Discovery Museum, Harbour Bridge pedestrian walk, MCA, Observatory, Botanical Gardens, Government House (guided tour), Art Gallery of New South Wales, State Library, Town Hall, St Andrews/Mary’s Cathedrals, Anzac memorial, Hall of Champions, free walking tours (tip welcomed and not could do better!!) and shuttle bus 555 on city centre loop.