The Tetrahedron in the city of Bottrop is a walkable steel structure in the form of a tetrahedron with a side length of 60 metres, resting on four 9-metre-tall concrete pillars. It is located in Bottrop, Germany, on top of the former coal mine dump Halde Beckstraße.

Also located in Bottrop, Prosper-Haniel was one of the last two active hard coal mines in Germany until its closure in 2018. The post-war economic boom (Wirtschaftswunder) in the country was mainly fuelled by hard coal mined in the states of North Rhine-Westphalia and Saarland, which powered the industries of West Germany. In the late 1950s, German hard coal lost its competitive edge and could no longer compete with cheaper imported coal. Eventually, the European Commission succeeded in its push for an end to Germany’s extensive coal subsidy schemes. In 2007, the federal government and the state governments of North Rhine-Westphalia and Saarland agreed with the mining company RAG and the trade union IG BCE to phase out hard coal mining subsidies in the country by 2018. The last two remaining hard coal mines in North Rhine-Westphalia (the other one was in Ibbenbüren,) were to close down at the end of 2018.

Meanwhile, the city of Bottrop has built an indoor ski slope near the popular Tetrahedron lookout tower, built on top of a mine dump, to demonstrate how mine dumps can be given a new lease of life.

Bottrop is also leading by example in a different field. The river Emscher flows past the city of Bottrop on its way from Dortmund through the Ruhr region/Emscher Valley to finally meet the river Rhine near the city of Dinslaken. Once the dirtiest river in Germany, polluted especially by mining and heavy industrial activities in the region, which discharged mostly untreated wastewater directly into the stream, it is now recovering through a multi-billion euro renaturalisation project called ’Emscher Conversion‘. At the heart of this project, which started in 1992, is the construction of a 51-kilometre underground wastewater canal, which follows the course of the river Emscher, but now fully separates stream water and wastewater from its riparian zone. Furthermore, a number of wastewater treatment plants have been built or upgraded along the river. The project is expected to be concluded by 2020 at a total cost of five billion euros.

• Further reading: CLEW factsheet on coal in Germany
• CLEW research tour: Germany's historic coal year 2018
• Date of publication: June 2018