Katy Perry was left with a "heavy" heart after visiting the Auschwitz-Birkinau State Museum.
The 'Roar' hitmaker took the time after her show in Krakow, Poland to visit the site of notorious concentration camps Auschwitz I and Auschwitz II-Birkenau, where over a million people were killed during the Holocaust, and the trip had an emotional effect on her.
Alongside a picture she took from the grounds, Katy wrote: "My heart was heavy today."
She then added the text from the site's memorial plaque, which reads: "For ever let this place be a cry of despair and a warning to humanity, where the Nazi murdered about one and a half million men, women and children mainly Jews from various countries of Europe. Auschwitz - Birkenau 1940-1945."
The 30-year-old singer recently spoke of how proud she is to have an "authentic" voice on social media.
She said: "My Twitter is very obviously run by me. So when you follow my Twitter, there is an authenticity that you sign up for. It's not my management, it's not the record label, it's not me selling a product to you all the time, every single tweet. I think that what people like is that they get tidbits of my life. I always keep them updated on what is going on."