During some down time on the European leg of her Prismatic World Tour, Katy Perry visited the notorious concentration camp, Auschwitz-Birkenau, in Poland, where Nazis killed an estimated 1.1 million people during the Second World War.

Katy Perry
Perry paid a visit to Auschwitz duing the European leg of her world tour

While the 30-year-old singer stopped by the World War II landmark site on Wednesday (Feb 25th), a day after performing at the Krakow Arena in Poland, she uploaded a photograph of the prison barracks to Instagram and shared a rather sombre message.

"My heart was heavy today. Forever let this place be a cry of despair and a warning to humanity, where the Nazi[s] murdered about one and a half million men, women and children mainly Jews from various countries of Europe," her caption read.

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"Auschwitz - Birkenau 1940-1945 'The one that does not remember history is bound to live through it again' George Santayana,'" she added, quoting Spanish-American writer George Santayana.

Perry, who performed in Vienna, Austria, on Thursday night (Feb 26th), shared the tribute just one month after the 70th anniversary of the liberation of Auschwitz. Her message was similar to that of the camps survivors, who urged that the world shouldn't forget about the atrocities that happened at Auschwitz.

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"People forget what Auschwitz was," Halina Birenbaum, who was held in the camp as a young child, told The New York Times, "and that terrifies me, because I know to what kind of hell it leads."