Port Jackson, better known as Sydney Harbour, is one such ria.
The Sydney area lies on Triassic shales and sandstones.
At a time in the past, monocline formed to the west of Sydney.
The monocline is a sloping bend that raises the sandstone well above where it is expected to be seen, and this is why the whole of the visible top of the Blue Mountains is made of sandstone.
The Hacking River is further south and runs through The Royal National Park into Port Hacking which forms the southern boundary of the Sutherland Shire.