To remove impurities, such as rock fragments, from the mined coal, a system was developed to 'wash' the coal. In a coal washing plant, the mined coal was introduced into an installation containing a grate at the bottom. Water was added along this grate in pulsating movements. Chunks of feldspar lay on the grates. Due to the pulsating movements (the washing machine), the coal moved over the bed of feldspar. The heavier rock sank up and through the bed and ended up on the grates.

This coal washing plant was built in the mid-1950s. It remained in service for the surrounding coal mines for nearly 20 years. The building has since been classified as a monument. It underwent an exterior refurbishment because there were plans to turn it into a public building. However, after an investment of 13 million euros, the works came to a standstill because there was no longer any room in the budget. There is now an intention to declassify the interior of the building so that it can be sold on the private market…

When you enter this building, you see almost immediately why it was given the name 'House of Escher'. The building contains a tangle of concrete staircases that seem to lead everywhere and nowhere. The association with the world-famous lithograph by graphic artist MC Escher, 'Climbing and Descending' (1960), is easily made.

'Climbing and Descending' is based on the 'Penrose staircase', an optical illusion and an impossible object conceived by the British mathematician and physicist Roger Penrose in 1958.