From Halopedia, the Halo wiki
Siófok is a location on the planet Reach. It is both home to the Siófok Firing Range and a facility that produces the R7 thrust coupling.
In the summer of 2552, Siófok was attacked by Covenant forces.
Like many places on Reach, it is named after a Hungarian town on Earth. Siόfok is a city in Hungary near Lake Balaton, the largest lake in Central Europe.