The lake Gårdsjön catchment is 2.1 km2 and includes 5 lakes and a number of headwater streams. It is located 50 km north of Göteborg. The whole area has been intensively studied for the last 30 years by scientists from IVL and from other institutes from Sweden and from abroad. Since 1979 several both national and international projects have been carried out. Smaller sub-catchments were used for experiments ranging from clear cutting, liming, fertilisation, sulphur addition and a combination of these treatments. In 1989 two large manipulation experiments were initiated. In the “Roof” experiment catchment G1 was covered by a transparent plastic roof and for 10 years the polluted precipitation was substituted with clean artificial precipitation sprinkled under the roof in a de-acidification experiment. The adjacent catchment G2 has been fertilised with NH4NO3 since 1991 to study several aspects (soil, water, vegetation) transition from N limited to N saturated conditions. Research at Gårdsjön resulted in three books and a large number of publications, covering different environmental problems, a range of pollutants, aquatic and terrestrial parts of the catchment, soils, vegetation and organisms. The site has served as an educational centre with countless visitors both from Sweden and abroad.