The Mages Guild in The Elder Scrolls IV: Oblivion has guild halls located in almost every major city in Cyrodiil. The main headquarters is the Arcane University in the Imperial City, which serves as the central hub for the guild and where you can access advanced features like spellmaking and enchanting

. Here are some key points about the Mages Guild locations:

• Imperial City : The Mages Guild is at the Arcane University, the main headquarters and the place to become Arch-Mage

• Other Cities : Each major city has its own Mages Guild hall, usually near the Fighters Guild. For example:
  • Anvil (leader: Carahil)
  • Bravil (leader: Kud-ei)
  • Bruma (leader: Jeanne Frasoric)
  • Cheydinhal (leader: Falcar; specializes in Alteration magic)
  • Chorrol (leader: Teekeeus)
  • Leyawiin (leader: Dagail)
  • Skingrad (leader: Adrienne Berene)

The guild hall in Kvatch was destroyed during the Oblivion Crisis and is no longer accessible

. To join the Mages Guild, you need to visit any of these local guild halls in the cities outside the Imperial City and speak to the guild leader there. After completing recommendation quests from each city’s guild leader, you gain access to the Arcane University in the Imperial City and the full benefits of the guild

. In summary, the Mages Guild is found primarily at the Arcane University in the Imperial City, with local guild halls in most major cities across Cyrodiil, except Kvatch where the hall was destroyed