The Duke and Duchess of Cambridge have described their visit to a Nazi concentration camp as a "terrible reminder of the cost of war".
William and Kate said their time at the Stutthof camp, near to the Polish city of Gdansk, had been a "shattering" experience.
During the trip, the royal pair heard first hand about horrors which befell the Second World War camp - in which 65,000 people lost their lives - from 1939 onward.
They came face to face with piles of shoes of Holocaust victims, tiny wooden huts used as sleeping quarters, and other evidence of Nazi attempts to exterminate the Jews.
William and Kate also saw the site's crematorium, once used to burn the bodies of thousands of prisoners.
Their tour of the camp formed part of a five-day foreign tour incorporating both Poland and Germany.
As they made their way around the site, William and Kate appeared to be in a sombre mood.
Towards the end of their trip they left a message in the visitors' book which both signed: "We were intensely moved by our visit to Stutthof, which has been the scene of so much terrible pain, suffering and death."
Their message continued: "This shattering visit has reminded us of the horrendous murder of six million Jews, drawn from across the whole of Europe, who died in the abominable Holocaust.
"It is, too, a terrible reminder of the cost of war. And the fact that Poland alone lost millions of its people, who were the victims of a most brutal occupation.
"All of us have an overwhelming responsibility to make sure that we learn the lessons and that the horror of what happened is never forgotten and never repeated."
Three-year-old Prince George and Princess Charlotte, two, joined the royal couple later for a trip to port city Gdansk, where they were greeted by large crowds.