The Prince of Wales stressed the possibilities inherent in breaking down barriers on a Northern Ireland visit that took in a cross border hospital and a centre dedicated to one of his favourite poets.
Charles and the Duchess of Cornwall began a four day trip to the island at a gleaming new facility dedicated to the memory of late Nobel Laureate Seamus Heaney.
Later the Royal couple travelled to Derry to meet cancer patients from both sides of the Irish border at a treatment unit that has been hailed a shining example of north-south co-operation.
The £50m facility at Altnagelvin hospital is jointly funded by health authorities in Stormont and Dublin.
As well as treating patients from the north west of Northern Ireland, it also enables people from Co Donegal to make the short trip across the border to receive care, rather than travelling large distances to hospitals in Galway or Dublin.
Earlier, addressing a packed conference hall at the Seamus Heaney HomePlace in the poet's native Bellaghy, Co Derry, the Prince said "varied histories, voices, and traditions" could create "all the greater harmony" when brought together.
"After all it is differences that make harmony possible, even as it is the barriers that have been overcome to make friendship all the stronger," he said, alluding to Northern Ireland's emergence from conflict.
The Prince is a big fan of Heaney and was recorded reciting one of his poems - The Shipping Forecast - for the exhibition centre in Bellaghy that celebrates his life and work.
Heaney said his rural childhood in his home village was the source of the extraordinary memory-hoard from which his greatest work sprang.
He was buried in a churchyard in the village in 2013 after a life lived in Dublin and around the world.
After closing their first day of engagements by attending a cultural performance at Hillsborough Castle, the Royal couple will head to Belfast on Wednesday where they are due to officially open a memorial garden to members of the Police Service of Northern Ireland (PSNI) who lost their lives on duty.
Later in the day they will travel south to the Irish Republic.
The Prince has officially visited the Republic of Ireland four times before, most recently in May 2016.
In 2015 they travelled to Mullaghmore in Co Sligo where the Prince's great uncle and mentor Lord Mountbatten and three others were killed by the IRA in 1979.
Highlights of the couple's latest visit to Ireland will include an engagement at Kilkenny Castle, where they will see some traditional music and watch a hurling demonstration by the Gaelic Athletic Association (GAA).
Charles will tour the United Nations Training School Ireland at the Curragh Camp, while Camilla will visit the Irish National Stud. Both will attend ceremonies at Glasnevin Cemetery in Dublin to commemorate those who lost their lives in the First World War and during the Easter Rising.
Irish President Michael D Higgins will meet the Royal couple in Dublin.
Whilst in the city, the Prince will also meet Irish Taoiseach Enda Kenny and he and the Duchess will conclude their visit by attending a reception at the British ambassador's residence.
The trip to Ireland is at the request of the British Government.
A statement from Clarence House said: "This visit will showcase the strength and vitality of the connections between the United Kingdom and Ireland; and the friendship and partnership that has defined our relationship over recent years."
At Hillsborough Castle the Royal couple enjoyed an evening of music.
The Music and Words for a Spring Evening event saw the world premiere of a new piece by Belfast composer Neil Martin, which was commissioned by Charles.
As part of a packed programme the Royal couple were also entertained by the children of the Tir Na n-Og School of Irish Dancing.
Tir na n-Óg Irish dancers Belfast entertaining The Prince of Wales & The Duchess of Cornwall here at Hillsborough Castle pic.twitter.com/ixBaam7GjH— Kevin Sharkey (@tv_KevinSharkey) May 9, 2017