The city authorities have announced that there will be two main areas for public viewing of the Euro 2024 games.

There will be a 'Football Village' set up in the Altstadt (Old Town), where matches will be shown on big screens and "Cologne’s diverse and colourful cultural scene" will be showcased. 

The main location for public viewing, however, will be the Tanzbrunnen on the far side of the Rhine in Deutz (marked on the map below). It will offer more big screens, plus several football pitches for schoolkids etc. to hold their own tournaments and simply enjoy playing the beautiful game.

More info here: Euro 2024 public viewing in Cologne.