1N-COUNT (持共同态度或信仰的人的)大本营,据点 If you say that a place or region is a stronghold of a particular attitude or belief, you mean that most people there share this attitude or belief. (持共同态度或信仰的人的)大本营,据点
The westernmost part of north Wales is a stronghold of Welsh-speakers.
2N-COUNT [with poss](某种动物的)主要栖息地 If you say that a place is a stronghold of a particular type of animal, you mean that more of that type of animal live there than in other places. (某种动物的)主要栖息地
Shetland is the last stronghold of otters in the British Isles.