Between July 1937 and April 1945, the Nazis imprisoned a quarter of a million people in the Buchenwald concentration camp, located near the German city of Weimar. Around 56,000 of them were killed before the camp was liberated by U.S troops on April 11, 1945. 68 years later, Reuters photographer Lisi Niesner interviewed some of the remaining survivors as they returned to Buchenwald to mark the anniversary of the liberation.

Holocaust survivors remember the horrors of Buchenwald concentration camp

File photo of a filing cabinets at International Tracing Service the world's biggest Holocaust archive in Bad Arolsen. ALEX GRIMM/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Candles and a cross are seen through a hatch at the detention cell building at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Concentration camp survivor Pusztai from Hungary sits in a wheelchair in front of the memorial side of a reconstructed gallows and a stone quarry barrow at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Concentration camp survivor Nussbaum from Romania stands in front of the memorial side of the Camp Gate at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

The memorial for all inmates of Buchenwald is pictured at the former muster ground in front of the camp gate building at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

A picture taken in 1945 hangs on the wall inside the pathology building adjacent to the crematorium at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Urns are displayed in a room adjacent to the crematorium at former concentration camp Buchenwald. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Relics found at former rubbish heap dump II are displayed at the historic exhibition at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

A historic picture of a general view of the concentration camp Buchenwald is displayed at the historic exhibition at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Historic pictures of inmates of several concentration camps are displayed at the historic exhibition at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

A wooden barrack is pictured behind trees at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

The clock set to the time of liberation of the Gate Building at former concentration camp Buchenwald is pictured near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp
Holocaust survivors remember the horrors of Buchenwald concentration camp

Roses are left on a memorial stone at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Concentration camp survivor Karpus from Ukraine is portrayed at the Muster ground in front of the Crematorium at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Dissecting facilities are pictured inside the pathology adjacent to the crematorium at former concentration camp Buchenwald. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Slovakian born concentration camp survivor Fuerst from Israel stands in front of the memorial side of the Camp Gate at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Polish born concentration camp survivor Silberstein from Israel stands at the memorial side of the Muster Ground at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Concentration camp survivor Mischtschuk, 87, from Ukraine stands near the memorial side of the Little Camp at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Holocaust survivors remember the horrors of Buchenwald concentration camp

Polish born concentration camp survivor Silberstein from Israel displays his tattoo with the number 68743 from Auschwitz at former concentration camp Buchenwald near Weimar. LISI NIESNER/REUTERS

Apr 17, 2013