Imperial City Dungeon
The Imperial City Dungeon, located on a separate segment of the Imperial City and connected by a stone bridge, is a storied place of myth and history. It is in truth most notorious for an absolutely factual historical event that tore at the heart of the Empire of Tamriel and ended the very Septim line of Emperors: it is the site of the assassination of Uriel Septim VII at the end of the Third Era, by the daedric cult known as the Mythic Dawn. Thus began the Oblivion Crisis, a far scarier tale than any myth told about these old dungeons.
The site held the offices and main barracks of the Imperial Legion outfit stationed in the Imperial City. The structure occupied by these facilities was very similar to that occupied by the Arcane University of the Mage's Guild, as almost a stone island connected to the main body of the city by a stone bridge. The dungeon itself was connected to the sewage system of the city, lending itself to a number of escapes; the most famous escapee via this route was the very Champion of Cyrodiil, who rescued the Empire from the Oblivion Crisis and solved a great many problems ongoing in the province at the time.