The Mechelen transit camp, officially SS-Sammellager Mecheln in German, also known as the Dossin barracks, was a detention and deportation camp established in a former army barracks at Mechelen in German-occupied Belgium. It served as a point to gather Belgian Jews and Romani ahead of their deportation to concentration and extermination camps in Eastern Europe during the Holocaust.
The camp was established in March 1942 and was the only transit camp in Belgium. It was managed by the Sicherheitspolizei, a branch of the Reich Security Main Office, and was used to hold Jews and Romani ahead of their deportation to Auschwitz-Birkenau as well as other camps including Heydebreck-Cosel. Between 4 August 1942 and 31 July 1944, 28 trains left from near the camp and deported over 25,800 people.
Wikipedia https://en.wikipedia.org/wiki/Mechelen_transit_camp
Coordinates 51°2'2.745" N 4°28'40.343" E