Cardiff's Principality Stadium will become a 2000 bed field hospital to help doctors fight the coronavirus outbreak.
The Cardiff and Vale University Health Board says 'work has already started' to adapt the home of Welsh rugby to a temporary hospital.
In a statement, the CEO of the health board said the decision had been made after looking at the predicted numbers of patients who might fall ill with the virus.
Len Richards said it was 'difficult to appreciate the size and scale of the task ahead of the NHS.'
He said that while he hoped that not all the beds would be used, the new facility would allow the board to 'free up' capacity at its other main hospital sites, allowing doctors to treat non-coronavirus patients.
A £350m 'super hospital' being built in Cwmbran will open a year early in a bid to tackle coronavirus.
The Grange University Hospital was due to officially open next year, but Aneurin Bevan University Health Board (ABUHB) revealed part of it will open in April to "provide up to an additional 350 beds".
The Cardiff and Vale University Health Board said it hopes it doesn't need to use all of the capacity being built.
The boss of the Welsh Rugby Union - which owns and operates the stadium - said the union was making the entire venue available to the health board, including "hospitality areas and a variety of further rooms and facilities."
Martyn Phillips claimed that plans were "advanced" to transform areas of the iconic 72,000 seater stadium into "fully functional hospital environments."
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