From Halopedia, the Halo wiki
Mimir was a city on the colony of Paris IV.
At some point before 2549, Molly Patel's family chose to live within driving distance outside the city.
In 2549 during the Siege of Paris IV, the Covenant Empire glassed the city. Some of the city's skyscrapers were destroyed in this process.
Mimir is a god in Norse mythology.