If you are going to ride around Sydney, one trail you will definitely end up on will be the Cooks River trail. The Cooks River before Sydney got big, ran from Chullora near Bankstown to Botany Bay. It used to consist of lots of marshlands and was probably a pretty good source of water to the original owners of the land. In the 20th Century we stuffed it up. We emptied all kinds of crap into to it, added lots of concrete and not much of the marshlands remains. We still continue to abuse it but its getting better slowly. At least we keep a lot of greenland around the creek and we built a shared path for cyclists and walkers that runs all the way from Strathfield to the Airport. This path helps promote the need to repair this important river.
One of the features of the path is the many bridges. Two of them are railway bridges, a few are car bridges and quite a lot are pedestrian/cycle paths. In this photo fest, I show all the bridges starting at Botany Bay upto to Punchbowl Rd where the creek turns into a concrete stormwater drain. Interesting is in all that distance, the drop in height is from 14m down to sea level. In otherwords the trail is flat.
That is now, listen to the history of the river on the ABC here >>
Read more here
https://cyclesydney.wiki/sydney/cooks-river/
Here is the map of the preferred Cooks River trail in purple starting at the airport >>