 Complete the following phrase:  Treblinka I was a gravel quarry equipped with heavy machinery, essential to the production of concrete and road construction. Before the German occupation, the mega quarry was owned by the Polish industrialist Marian Łopuszyński who built a railway track connecting the mine with MałkiniaSokołów Podlaski junction. Setting up a penal colony there was the idea of Sturmbannführer Ernst Gramss who first ran it as his own personal business venture in occupied Poland. The quarry became vital during the German 