The main geothermal resources of Austria (area 83,858 km², 8.05 million inhabitants in 2002, capital city Vienna) are in the sedimentary basins bordering the Eastern Alps (Styrian Basin, Upper Austrian Molasse Basin, Vienna Basin). In the 1977-2004 period, a total of 63 geothermal wells with a cumulative length of some 100 km have been drilled. A high percentage of these wells were intended for balneological use (thermal spas, curing, leisure resorts, hotels). The development of spas had an enormous economic impact especially in the Styrian Basin in SE Austria, where eight new spas were built between 1977 and 2004. Approximately 3.5 million guests visit the thermal spas per year