Umslagplatzmeans transfer point, the place in the Warsaw ghetto where the Jews were assembled for deportation.
The Umslagplatz, located at the corner of Zamenhof and Niska streets, was the area dividing the Warsaw ghetto from the Polish part of the city. From this location hundreds of thousands of Jews were deported to extermination camps and concentration camps--mostly to Treblinkabetween July and September 1942 and January and May 1943.
In 1988 a monument was erected on the site where some 300,000 Warsaw Jews were sent to their deaths.
Source: Encyclopedia of the Holocaust.