Hollywood couple Catherine Zeta Jones and Michael Douglas have officially opened the first phase of the Children's Hospital for Wales.
They unveiled a plaque and talked to patients on a tour of wards in Cardiff.
Actress Zeta Jones is a patron of the Noah's Ark Appeal - set up to raise funds for the hospital.
She said she was "very proud" but that fund-raising and campaigning would continue towards the next phase of the £21m unit.
More than 3,350 patients have stayed at the unit on the University Hospital of Wales site in its first year following its opening in March 2005.
The hospital has also treated another 1,955 outpatients and 625 day cases.
The Noah's Ark Appeal was launched in 2000
Zeta Jones, who also attended a fund-raising dinner on Monday night, said: "This is just the beginning stages.
"We have a lot more work to do and more campaigning to do and I'm just very proud that we now have our designated children's hospital in Wales - there are children who can have the best treatment and care, and it makes me very proud."
Douglas, wearing a grey suit said that the hospital looked "stunning".
Zeta Jones, along with fellow patron Charlotte Church, joined cricket legend Ian Botham on a fundraising walk to raise money for the hospital in 2002.
And in 2005, Zeta Jones and Douglas donated a five-figure sum to the Noah's Ark Appeal.
The first phase of the hospital development includes two 25-bed medical wards and one 16-bed paediatric cancer ward.
A second phase for the children's hospital is now being planned at the site.
Around £7m has been raised by the Noah's Ark Appeal for the hospital, which is expected to cost a total of £21m.
It is the first hospital set up Wales specialising in the treatment of sick children. Zeta Jones said: "It's lovely to be back home."
But she also said she would be supporting the England team in the World Cup and had a message for them, saying: "Go boys."
The couple attended a charity dinner in Cardiff on Monday night
She is hoping to see the semi-final and hopes that England will be playing.
The Hollywood pair met 11-year-old patient Ben Miles.
Zeta Jones stroked Ben's leg and told him she liked his diamond ear stud.
Ben's mother Lisa Miles, from Llanrumney in Cardiff, said of the hospital: "It's very nice."
Sue Morgan, directorate manager of child health, said the hospital aimed to provide a child-friendly environment as well as a place which supports families through difficult times.
"We are grateful to everyone who has supported the development from the start and are delighted that Catherine Zeta Jones and Michael Douglas have both taken the time to visit the wards today and meet the patients, their families and staff," she said