The Imperial Prison is the jail in the Imperial City and is the largest prison in the game. There are various quests involving it. The dungeon of the Imperial Prison is the starting point of The Elder Scrolls IV: Oblivion. The jail also holds Valen Dreth and Claudius Arcadia prisoner. Depending on Player choices in Oblivion, the player may have to infiltrate the prison to kill Valen Dreth — the Player must be in the Dark Brotherhood and if the player does not kill any guards, then a bonus is received (though the Player may have to use an invisibility spell such as Ghostwalk to get the bonus award).
A main quest that people must complete is the opening Quest in Oblivion, where the Player finds his or her way out of the prison via a secret escape route that is also in use by Emperor Uriel Septim. Another quest is the Dark Brotherhood Quest, in which the Player infiltrates the Prison to locate and kill Valen Dreth, an old and weak Dunmer who formerly teased the Player during the opening tutorial.
- On one of the walls in the dip where the secret passage descends, there is a tally adding up to 23. From this, it could be inferred that the Hero of Kvatch was imprisoned for 23 days before his or her escape.