An oil platform in Mittelplate, the largest oil field in Germany. The field is located in the North Sea, around 7 km (4.3 mi) from the shore, in the tidal flats of the Schleswig-Holstein Wadden Sea National Park. It was discovered in 1980 and 1981 when test borings in the Mittelplate vicinity found oil in several sandstone layers. Due to the location of the field in an ecologically sensitive area it was subjected to hydrographic, hydrodynamic and meteorological studies to model storm, wave, and ice-flow conditions. The results led to the construction of an artificial island in 1985, which holds a drilling and production facility. By the 20th anniversary of the start of production, 20 million tonnes of crude had been produced from the field.Photograph: Ralf Roletschek