Buchenwald concentration camp
The SS left behind records of how many prisoners came to the camp and how many left.  They recorded how many prisoners were let go, sent to another camp, or died.  These records say that 33,462 prisoners died at Buchenwald.  However, these records may not be completely true.  For example, before 1944, when the SS killed prisoners, they often wrote down that the prisoners were "transferred to the Gestapo," not that they were killed.  Also, starting in 1941, many Soviet POWs were executed in mass killings.  These POWs would be killed as soon as they got to the camp, and were never added to the camp's records.  This means they were not listed among the 33,462 dead.