Lobau is one of my favorite places in Vienna in summer. It is that forest in Donauinsel called Lobau.
How to reach there?
You have connectivity in 3 metro lines to Lobau – U2 Donaustadtbrucke, U1 Donauinsel, U6 Neue Donau. If you prefer walking in the forest then you can either choose the U2 or U1 line stops. If you would riding through a bicycle then you can choose any of the stops.
I personally prefer starting from DonauInsel in bicycle. You can carry bicycles all through the day on weekends or on holidays in the metro lines. But on week days you are not supposed to take the bicycles in metro trains till 9 AM in the mornings and from 3 PM to 6.30 PM in the noons.
I usually take my bicycle to Donauinsel on a weekend day in the evening and start riding towards U2 line. That is the direction opposite to the Kahlenberg.
There are many cycle paths on both sides of the Donauinsel river. Also you can either ride along the shore of the DonauInsel canal or ride between the trees in the forest. The main Donau river runs between VorgartenStrasse U1 line and Donauinsel U1 line. A little part of the river is let to form the Donauinsel canal.
There is a dangerous point in the very end of the cycle trail. And this where you can see the water from the main river is let to form the Donauinsel canal.