Thousands gathered in Cardiff Bay in 2008 to watch the FA Cup Final
Football fans will be able to watch Cardiff City's Championship play off-final at Wembley on a big screen in Cardiff Bay.
Seven thousand people will be allowed into Roald Dahl Plass on Saturday to see if the Bluebirds beat Blackpool to clinch promotion to the Premier League.
Admission will be free on a first come first served basis from 1300 BST.
Rugby fans will be able to see Cardiff Blues v Toulon in the Amlin Challenge Cup Final on the screen on Sunday.
Cardiff City fans will be hoping for a better result than in 2008 when a similar big screen event was staged for the FA Cup Final.
The Bluebirds lost that match to Portsmouth.
The screen will be showing live coverage of all the big match build-up from 1400 BST, staying on air until half an hour after the game ends.
The council promises a family friendly event to mark the occasion
For health and safety reasons no-one will be allowed to take alcohol onto the site.
Cllr Nigel Howells, Cardiff council's executive member for sport, leisure and culture said: "We want to make sure that as many people as possible who want to have the chance to watch the match in a family-friendly environment can come along and see the Bluebirds take on Blackpool.
"I'm sure the atmosphere will be electric with everyone getting behind Cardiff City to win and get into the Premier League.
"Roald Dahl Plass is a fantastic location for the big screen. It's going to be a great day and we are delighted to be working with South Wales Police and the Harbour Authority to ensure we can provide this facility."
The area will reopen on Sunday at 1300 BST for a live relay of the Amlin Challenge Cup Final between Cardiff Blues and Toulon in Marseille.