From Halopedia, the Halo wiki
Erőd was a city on Reach. Rajtom Facility was located just outside the city, utilized as a research and development facility of Misriah Armory.
The city shared its name with the Erőd-class orbital weapon platform.
"Erőd" is a Hungarian word meaning "fortress" or "stronghold". It is also the name of one of the available skins for the INDOMITABLE-class Mjolnir armor.