Alfea

The Alfea School for Fairies is a young girl's boarding school in Magix for fairies in training ages 16-19 (unless they have been held back a grade like Stella, so in her case 20). All of the Winx girls met and resided here and have a close relationship with its headmistress, Ms. Faragonda. Fairies here learn how to control their power, fight evil, learn new spells as well as be guardians of their planets, or in many cases, learn how to be their realms' queens.

The age at which Fairies and Witches respectively join Alfea and Cloud Tower is 16 years old, and it is at this age that Bloom first discovered her powers. It could be that it is at this age the magic powers of the Fairies and Witches start appearing and that they can still chose, like Mirta did, between becoming either a Fairy or a Witch so long they have not reached the level of full-fledged Fairies or Witches.