All Civilizations can build a barracks. A barracks allows players to train additional infantry and cavalry units and contains infantry and cavalry training upgrades.
The Britons, Celts and Gauls barracks provides a Population Bonus of 4. Also, their barracks doesn't cost any stone.
The Hellenes barracks while requiring stone and taking longer to build, is slightly more resiliant with 10% more HP.
The Persians barracks doesn't cost any stone. Unlike the other civilizations, they can't train any cavalry in their barracks either. Instead, they train cavalry at their Stables.
The Mauryans barracks doesn't cost any stone.