||Sincemany years, mountain biking has become a popular activity. In the late 1990s, more than 800 km of mountainbike trails werelaid in theWienerwald, Lower Austria and Vienna. Since then the demands of mountainbikers have changed, because besideshardtail mountainbikes, downhillbikes and fullsuspensionbikeshave also gained importance. In the last few years various non-designated single trails in and around Viennahave become popular and many off-trail areas (areas with illegally built ramps and jumps by the users themselves)have developed.Interviews (e.g.Reimoseret al., 2008),observations (Arnberger and Eder, 2007) and analysisof available online GPS-user data (e.g. heat maps) show that non-designated trailsare sought out by mountainbikers.