The first executions in the forest of Niepołomice took place as early as 1939, of officers and soldiers of the regular Polish army. From 1941 onwards, Soviet, French and Italian prisoners of war were also executed there. In October 1943, after a clash between the guards and the prisoners of the Kraków Płaszów camp, during which the Italians defended the prisoners, a mass execution took place, in which all met their death.
The largest execution took place from 10 to 15 December 1943 at Kozie Gorki, in the forest of Niepołomice; the Germans massacred nearly a thousand people from Kraków, Gdów, Dobczyce, Niepołomice and Wieliczka, among whom many monks and priests, French prisoners of war as well as Italian officers and soldiers. Among those murdered were members of the Kraków intelligentsia, arrested and imprisoned in the Montelupich prison, then brought to the forest during the night to be executed there. Notably among them was Stanislaw Klimecki, mayor of Kraków. The victims were forced to dig their own grave before dying from a bullet to the back of the neck. Pines were planted over the mass grave to conceal the place of the execution.
In the aftermath of the war only a wooden cross remained. In 1960, an obelisk was erected to commemorate this tragic event. On it one can read, in Polish: "This place is stained with the blood of about 1,000 Polish and foreign patriots, murdered by the Nazis in 1943." About thirty names could be identified () and were inscribed on a plaque, unveiled in December 2018. Not far away stands another monument, also very well maintained, on the site of the mass grave of the Jewish population shot by the Nazis on 26 and 27 August 1942. The Germans murdered around 700 Jews brought from Kraków and neighbouring towns. Among the victims was the entire staff of the Jewish hospital of Wieliczka.