Over the past four decades, research in the HADES underground research laboratory has made a major contribution to the assessment that geological disposal of radioactive waste in clay can provide a safe and feasible solution for the long-term management of high-level and long-lived waste in Belgium. On the occasion of the 40st anniversary of the HADES underground research laboratory, EIG EURIDICE, SCK CEN and ONDRAF/NIRAS prepared a Special Publication on “Geological Disposal of Radioactive Waste in Deep Clay Formations: 40 Years of RD&D in the Belgian URL HADES“, edited by X.L. Li, M. Van Geet, C. Bruggeman and M. De Craen. This Special Publication presents the main contributions of the HADES laboratory to Belgian and international research into geological disposal. This Special Publication is available in open access. It can be accessed via EURIDICE website (www.euridice.be “in the spotlight” – “HADES40 Special Issue”), by clicking the image below or directly at the webpage of the Geological Society Special Publications (https://www.lyellcollection.org/toc/sp/536/1). It is also possible to buy a print book via this website.