By Barbara Erling and Kuba Stezycki OSWIECIM, Poland (Reuters) -Auschwitz survivors were being joined by world leaders on Monday to mark the 80th anniversary of the liberation of the Nazi German death camp by Soviet troops,

Silence pervades the site of Auschwitz-Birkenau today. Sometimes the only sounds are the soft footsteps of visitors, people who come from all over the world to mourn and to learn, and the voices of their guides speaking in hushed tones into microphones trying to explain the ungraspable.