Buchenwald’s first commandant (camp leader) was Karl-Otto Koch. He ran the camp from 1937 to July 1941. His second wife, Ilse Koch, became well known as "Die Hexe von Buchenwald" ("the witch of Buchenwald") for the terrible ways she treated the prisoners. Koch made the prisoners build a zoo at Buchenwald, with a bear pit ("Bärenzwinger").