As the world remembers the 60th anniversary of the liberation of Auschwitz and Birkenau, BBC Wales' Iolo ap Dafydd visited the site in southern Poland.
It is claimed that birds do not sing in Auschwitz since the Holocaust.
It is also claimed that the all-prevailing doomed atmosphere at both the Auschwitz and Birkenau camps will seep into one's soul.
Having witnessed both camps, which are now open-air museums, it is difficult not to agree.
In one newspaper recently, one article amongst the hundreds printed - and one quote especially - caught the eye.
There is also a mountain of human hair, shaven off corpses to be re-used as blankets
It was by a former British prisoner of war, Dennis Avery from Derbyshire, who was held in Poland near Auschwitz in 1944.
He is 86 years old with memories he would rather forget.
"Auschwitz was an evil place," he said.
"It felt evil and it tasted evil. The whole time I was there I never saw a bird or a bee or a butterfly."
This is one museum that sobers the mind, and rams home with a scientific approach the brutality and horrific indifference of the Nazis.
Within the 28 red-bricked barracks in Auschwitz, there are many sickening exhibitions.
Pictures of the victims of Auschwitz line the walls
Within some, all floors have been dedicated to the attack on Poland by Nazi Germany and the Soviet Union in 1939, and cataloguing the suffering and murders of the mainly Jewish, Roma and Polish civilians as well as the many Soviet prisoners of war killed in this camp.
The State Museum in Oswiecim , as Auschwitz is called in Polish, begins its guidebook with an understatement: "For five long years the name of Auschwitz aroused fear among the populations of the Nazi-occupied territories."
As a volunteer working in Kibbutz Nir Am in southern Israel in 1984, I saw the effect of that terror at first hand.
Late at night an elderly man would walk frantically around the grounds muttering to himself.
He would neither acknowledge anybody else, nor talk to them.
With his black six-number tattoo on his arm, I was told he lost his entire family in Auschwitz and was taken in when he arrived in Palestine after World War II.
Birkenau, with its railway tracks and vastly bigger site, is an even grimmer reminder of how many people were shot, tortured, gassed, burnt and killed.
Now there is not much to see, except the huge site with a few empty wooden barracks the Holocaust memorial and four bombed gas crematoriums blown up by the retreating Nazis.
But it is to Auschwitz first that the leaders of Poland, Germany, Israel and Russia, and many other political leaders will congregate on 27 January.
Here they will hear speeches by three former inmates, and a message from Pope John Paul, who lived then in the nearby city of Krakow. They will commemorate the liberation of Auschwitz-Birkenau by the Soviet Army in 1945, and note Holocaust Day as well.
The three former prisoners survived unimaginable horror. Almost 1.5m others did not.
Amongst them 1m Jews, 150,000 Poles, 23,000 Roma, 15,000 Soviet POWs and 10,000 others of various nationalities were exterminated in five years.
The only visible reminder of them in the densely sad and brooding atmosphere at the former concentration camps are the great mounds of shoes, clothes, reading glasses, suitcases and pots and pans they brought with them.
Pitiful belongings, which are now exhibited at Auschwitz.
There is also a mountain of human hair, shaven off corpses to be re-used as blankets. That and the ironic slogan they saw as they were marched in through its gates - arbeit macht frei.
Translated from German, it reads: "work brings freedom".
Iolo ap Dafydd presents BBC Wales' Week In Week Out and Radio Cymru's Post Cyntaf