Finally, after 16 years of trying to fish in Austria, I have found a way to do it legally. A license to fish anywhere in Austria is strictly enforced, with fishing rangers checking angler licenses and their tackle. It costs 31 euro to fish for 1 day in Vienna. What you also need is a fishing license, which you can buy for 5 Euro and is valid for 3 weeks. No exam is required.
As I live in Vienna, its approx 10min in the subway or 10min with my moped to the Danuabe River, which I have passed at least twice a day for the past 10 years. I chose the upper end of the Danube river, as it is quite secluded from the city and you get a sense that you are not in the city, except on the side of the river a motorway stretched over the Danube River. If you go further north of the Danube, you will feel like you are in the country side.