Previous studies have repeatedly recorded bats hunting in cities. During summer 2007, I conducted a detector survey in a densely built area of the city of Vienna, to map the hunting activity and correlate it to data of the urban biotope monitoring. Overall, we recorded 583 points with bat activity within an area of about 18 square kilometres. Parks and water bodies were intensively hunted, but also densely built areas were well accepted. I was not able to identify which factors contributed to high activity, but found a preference for wooded areas. So, the presence of even a few trees could possibly make cities more attractive for bats.