I was recently reading through the Sydney Gazette when I read a brief article published on 5 Jun 1803 stating that a new stone bridge was being built at the head of Sydney Cove. In other words, over the Tank Stream that fed into Sydney Harbour:
This map (with a German legend) from 1802 shows the layout of Sydney.
When we magnify in on Sydney Cover (now Circular Quay) item 22 ('Bridge' in German) is visible, the bridge at the head of Sydney Cove:
This painting from 1803 by John William Lancashire (dictionaryofsydney.org/image/40423) shows at the extreme right a STONE bridge, allowing water to pass under it, just as described in the newspaper article. Based on the article above, the painting with the stone bridge was surely rendered in the second half of the year!
Here is another painting from 'circa 1803', by George William Evans (http://acms.sl.nsw.gov.au/item/itemLarge.aspx?itemID=457903). In this case the wooden bridge can be seen, suggested it was rendered in the first half of 1803 (or earlier):
So you can see we can do a lot with just one small article in the Sydney Gazette.