It has been a common although the least rational practice for a lot of abandoned quarries to be used as sites for uncontrolled waste disposal. Such is the case of the Karens abandoned quarries in Athens. Greece. The area of Kareas. faced an intense quarrying activity during the 60s and 70s, though without any envirorniicntal consideration, thus causing the dramatic aesthetic degradation of the mountain's visible side. For the next twenty years, in the name of reshaping of the huge craters which had been created in the area, an uncontrolled disposal of constrution debris as well as municipal solid waste ( MSW) took place. Thus, the largest uncontrolled landfill in Greece was formed, stretching to almost 40 hectares, particulary in one of the most beautiftil sites of Athens As a result, new, more intense environmental problems appeared, such is landslide hazards, ground water pollution, visual pollution etc. This paper presents the overall methodology for the rehabilitation of the area, which.has proved to be a complicated scientific and technical, problem.