The new screen has been set up outside St David's Hall in The Hayes
Shoppers and workers will be able to catch all the action from the Olympics Games via a big screen in the centre of Cardiff.
The 25m square screen has been set up outside the city's St David's Hall on The Hayes and will screen coverage every day from 0800 until 2000 BST.
The screen forms part of a UK network known as Live Sites with more than 30 others situated around the country.
All the Games coverage will be supplied courtesy of the BBC.
The screens will also broadcast the London 2012 Olympic Handover Celebrations.
Each screen has interactive capabilities enabling each location to link up with one another as the action takes place.
The fixed locations will be used to show other major events to the public in the lead up to London 2012 and the Paralympic Games and beyond.
In the meantime, they will also broadcast a range of local information, news and major cultural, sporting, educational and community events.