The HADES underground research laboratory (URL) is located in Mol (Belgium) in the Boom Clay formation at a depth of 225 metres. HADES plays a central role in the Belgian research program into the safety and feasibility of geological disposal of radioactive waste. Experts use it to develop and test industrial technologies for building, operating and closing a waste repository in deep clay. Scientists conduct small and large-scale experiments under realistic conditions in the deep clay formation over a long period of time to assess the safety of geological disposal in poorly indurated clay. HADES is a licensed nuclear research facility, which means that scientists can use a wide range of radioactive tracers and sources. Since more than five years, the large-scale PRACLAY Heater test has been running to demonstrate the feasibility of geological disposal of high-level, heat producing waste in clay. HADES is the oldest underground laboratory in Europe built in a deep clay formation for the purpose of researching the possibility of geological disposal in clay. SCK CEN began the construction of the HADES URL in 1980. Since 1995 HADES has been operated by the Economic Interest Grouping EIG EURIDICE, a partnership between SCK CEN and the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF/NIRAS). In Belgium, ONDRAF/NIRAS is responsible for radioactive waste management and coordinates the geological disposal RD&D programme. This URL is open to technical visits and guest researchers.