Up to 250,000 fans have descended on Cardiff in the hope of celebrating a third Grand Slam victory in the last eight years.
The day was marked by a minute's silence before Wales' Six Nations international kicks-off against France, in memory of Mervyn Davies.
The former British Lions and Wales hero died on Thursday, aged 65.
Both teams wore black armbands as a mark of respect to "Merv the Swerve".
Moods have been tempered by the death of Davies, described by many as the best number eight ever to pull on a Welsh jersey.
He helped Wales to win two Grand Slams and three Triple Crowns, his performances leading to inevitable selection for the British Lions tours in 1971 and 1974.
But his career was cut short in 1976 when he suffered a brain haemorrhage while playing for Swansea against Pontypool in a Welsh cup semi-final.
The current assistant Welsh coach and former captain, Rob Howley, said the Wales team had been told of Davies' death on Friday.
"The players, the management, we all send our sincere condolences to the family," he said.
"We can speak frequently of world-class players, but icon and legend belongs to Merv the Swerve."
Howley also added that he hoped it would give the Welsh side added motivation for Saturday's game.
"It's emotional, I met him on several occasions when I was Wales captain and he gave me plenty of words of wisdom. He was a very humble man who knew the game inside-out."
Flags have been flying at half-mast at the Millennium Stadium following the announcement, but spirits will be lifted on Saturday if Wales beat France to win the Six Nations Grand Slam.
As the hundreds of thousands of fans flooded into the city, a supporters' village was set up complete with big screen at King Edward VII Avenue for those without tickets.
A big crowd was also expected to watch the match, which kicked-off at 14:45 GMT, on a screen in Swansea's Castle Square.
Arriva Trains Wales said there would be extra services running from north Wales and Gloucester and additional carriages and extra seating on the Valleys network and west Wales and Ebbw Vale routes.
A spokesman said following the game customers should head for Cardiff Central station as soon as possible as services will operate on a first come, first served basis.
He added: "The usual crowd management queuing system will be in place and customers are reminded to be mindful of this when planning their return journey as they could be queuing for up to an hour or more.
Cardiff council is urging those travelling into the city centre to use public transport where possible.
Those travelling by car are being asked to use the park and ride service based at Cardiff City football stadium.
There will be full road closures in the city centre between 12:45 GMT and 17:45 GMT.
The supporters' village is being set-up at King Edward VII Avenue rather than Coopers Field where it has been for previous Grand Slam deciders because of concerns about the weather.
It will open at 11:00 GMT and show all three final Six Nations games on the big screen.
The council's executive member for sport and culture Nigel Howells said for licensing reasons fans would not be allowed to take their own alcohol onto the site but there would be ample food and drink available.
"This is a huge match for the whole of Wales on Saturday and there will be a lot of people coming into the capital to soak up the atmosphere," he added.
BBC Wales weather forecaster Derek Brockway said there was a risk of showers in Cardiff on Saturday.
"There will be a few bright or sunny intervals but on the whole a lot of cloud," he added.