This is a great place to get your run in, should you need to. The lakes are encircled by running paths, and you would be in the good company of the many Wieners who feel that getting out and exercising when the weather is "frisch" is vital for one's health.
When you're finished you can ascend the tour for a stellar view or hang out on the many benches around the lake to watch old men play chess as if they've been in the same game since 1984.
Also nearby is the UNO-City, which is the United Nations building in Vienna. Most people don't realize how important a city Vienna was and has been on a diplomatic level. OPEC will even meet here on occasion, and, during the cold war, Russian and U.S. spies probably got together for some of Vienna's famous "servus" and "service" at one of the many legal brothels in the city.