The part of greater Sydney where I live in is blessed with one cyclepath, which goes north/south all the way from Cronulla to Brighton-Le Sands. It doesn't go further, because the tunnel under the airport landingstrip is not suitable for cyclists: Cars are driving in rows of four, each side, through it at 80 kilometers per hour. It surely was something they didn't think about when they build that tunnel. And it is quite a shame, because now you can't cycle all the way around Botany Bay.
A second cyclepath goes from east-west from Homebush Bay to Brighton-Le Sands. If you link these two, you end up with a cyclepath between Cronulla and Homebush Bay! Or in my case, from Caringbah to Greenacre. good for fourty kilometers.
In a city where cyclists are considered second-rate citizens, these kind of facilities should be cherished. They are made for recreational cyclists, you wouldn't want to do them every day: They are way too messy and clumsy and you can't make proper speeds on them. So euhm.... what do we have?
From Caringbah to over the Captain Cook bridge, it's industrial area backstreet. If you come from Cronulla you can take the cyclepath between Shark Park and Taren Point. Between Sandringham and Brighton-Le Sands it is shared with pedestrians and often very windy path. Add constantly bumps and having to move up and down from the footpath onto the road, it is less than optimal.
From Brighton-Le Sands to South Strathfield goes via the Captain Cook river. The first part goes south past a lot of vegetable patches, then north past the St George soccer field, under the M5 and there I got lost. But after I hit the Princes Highway and went north I found the river again. Going past the river is very nice and even on a hot day like today it was cool enough. The whole path is interrupted by crossings with roads where you have to break, stop, pass first part, pass second part, and start again. But it is doable. And if you have, or your pillion has, enough of it, there are enough parks with playground facilities on the road.
The Captain Cook river, at Brighton-Le Sands it is a big river, but the further and further you go it will shrink in size, until at the end you have a small stream of water, 30 centimeters wide, floating in a huge concrete bed.
The last part of the trip past the Captain Cook river ends at the crossing with the Hume Highway / Liverpool Road in Strathfield. There you again see the Sydney you know, with its asphalt and cars. Luckily the footpath is safe, and two kilometers further we were at the home of Dirkie's Australian grandparents where we spend the rest of the afternoon.
Cycling between Caringbah station and Kurnell is 13 kilometers, but you have to cycle back due to lack of train stations in Kurnell (but there is one in Cronulla and Woolooware).
From the train station, go to the Denman avenue because you will not be able to cross the railroad again until somewhere in Cronulla.
At the crossing of Denman Avenue and Gannoa Road, turn left. If you go straight, you unnecessary will go up a hill. Past Sharkies and the school and that's the last you will see from Cronulla.
The Captain Cook drive is a nice long road with only two minor hills but it has, despite that it is a beautiful natural area, one huge drawback: It is full with factories and industrial areas on the right hand side. I don't know who got the idea of putting all that industry here, but it surely is not the right place for it.
In Kurnell at the crossing of the Captain Cook drive and Polo street is a small milkshop which does do a very good milkshake. Take the milkshake into the National Park and enjoy it in the Memorial Park!
Cycling between Helensburgh station and Stanwell Park is another nice size trip (10 kilometers) with a stop at Symbio Zoo and Stanwell Heights.
But there is one major warning: From the station till Helensburgh town center it is only hill up. And hill up. And hill up. For about three kilometers. But once you are at the Symbio Zoo you have two hours to recover from it.
From Symbio Zoo to Stanwell Heights is a nice refreshing trip through the foresty areas, and at Stanwell Heights an unique view over Stanwell Park and if you're lucky you will see some whales.
Down from Stanwell Heights to Stanwell Park is a drop of 250 meters over 2500 meters, making it an interesting experience for the brakes on the back of your bike. And at the bottom you can enjoy a swim on the beach.
Be warned, going back to the train station in Stanwell Park is an only-hill-up experience too.
Cycling between Waterfall and Helensburgh is a nice size trip (10 kilometers).
You can go via the Southern Freeway but I would strongly suggest not to do this: You only have three hills, but these are horrible hills which don't give you any satisfaction. When you do it early in the morning you don't have too much hassle of the traffic going between Sydney and Wollogong.
The path you should take is via the Princes Highway, on which there are more hills but they are not that high. And it will give you more shadowed areas.