The area/district/state is a Republican 'stronghold'.
The rebels retreated to their mountain 'stronghold'.
the last 'stronghold' of the endangered deer
(..) and deep ravines of District . There in the heart of Panem's steepest mountain range lies the Capitol's principal military facility. We can conquer this stronghold because we are one people, one army, one voice. Because today is our new beginning. Today we have freed the Victors. Tomorrow, Panem! (..)2014 The Hunger Games: Mockingjay - Part 1