stronghold
n. countablen. a place that is very well protected and hard to attack. It can also mean a place where a specific group of people or a set of ideas is very popular.
n. a fortified place or fortress that is difficult to capture. By extension, it refers to a geographic area or social sphere where a particular belief, political party, or group maintains a dominant influence.
The castle was a powerful stronghold during the war.
The northern province remains a political stronghold for the opposition party, which has won every election there for twenty years.
While the coastal cities embraced the new cultural trends, the rural interior remained a stronghold of traditional values and ancestral customs.
From Middle English stranghalde, strong-hold, strong-holde, from strong (“having physical strength, sturdy, strong; built to withstand assaults, fortified”) (from Old English strang, strong (“strong”), ultimately from Proto-Indo-European *strengʰ- (“stiff, tight”)) + hōld (“grasp, grip; control, possession, rule”) (from Old English). By surface analysis, strong + hold.
Often used with the preposition 'of' to describe the group or idea that dominates the area.