To properly record and document and then to remember those who died in this terrible place.
For information cf. numerous sources including the following:
Belzec extermination camp - Wikipedia
https://en.wikipedia.org/wiki/Be%C5%82%C5%BCec_extermination_camp
Bełżec[2] (pronounced [%CB%88b%C9%9Bu%CC%AF%CA%90%C9%9Bt%CD%A1s], in German: Belzec) was a Nazi German extermination camp built by the SS for the purpose of implementing the secretive Operation Reinhard, the plan to eradicate Polish Jewry, a key part of the "Final Solution" which entailed the murder of some 6 million Jews in the Holocaust.[3] The camp operated from 17 March 1942 to the end of December 1942.[4] It was situated about 0.5 km (0.31 mi) south of the local railroad station of Bełżec, in the new Distrikt Lublin of the semi-colonial General Government territory of German-occupied Poland.[5] The burning of exhumed corpses on five open-air grids and bone crushing continued until March 1943.[6]
Between 430,000 and 500,000 Jews are believed to have been murdered by the SS at Bełżec.[4][7] This makes it the third worst extermination camp, exceeded only by Treblinka and Auschwitz. Only seven Jews performing slave labour with the camp's Sonderkommando survived World War II;[6] and only one of them became known,[8] thanks to his postwar testimony submitted officially.[9] The lack of viable witnesses who could testify about the camp's operation is the primary reason why Bełżec is so little known despite the enormous number of victims.[9]
And also e.g.
: Belzec Death Camp www.HolocaustResearchProject.org
http://www.holocaustresearchproject.org/ar/belzec.html
&
Museum – Memorial Site in Belzec