The Mechelen transit camp, officially SS-Sammellager Mecheln in German, was a detention and deportation camp established in a former army barracks at Mechelen in German-occupied Belgium. It was managed by the Sicherheitspolizei, a branch of the SS-Reichssicherheitshauptamt, in order to collect and deport Jews and Romani mainly out of Belgium towards the labor camp of Heydebreck-Cosel and the concentration camps of Auschwitz-Birkenau in German occupied Poland.
During the Second World War, between 4 August 1942 and 31 July 1944, 28 trains left from this Belgian casern and deported over 25,000 Jews and Roma, most of whom arrived at the extermination camps of Auschwitz-Birkenau. At the end of war, 1240 of them had survived.Since 1996, a Holocaust museum has been open near the site of the camp: the Kazerne Dossin – Memorial.
Wikipedia https://en.wikipedia.org/wiki/Mechelen_transit_camp
Coordinates 51°2'2.745" N 4°28'40.347" E