Cyrodiil is a province in the fictional world of Tamriel in the Elder Scrolls series.
It is the domain of the Imperial race. Geographically, it is in the center of Tamriel exactly. The huge Imperial City is home to the Emperor of Tamriel.
In the events of Arena, the player must fight Imperial Battlemage Jagar Tharn at the Imperial City in order to rescue the real Uriel Septim VII.
In the events of Oblivion, players explore Cyrodiil while fighting against the Daedra threat.