fastness

这座古老的城堡在危险时期曾是国王的坚固堡垒。

The ancient castle served as the king's ___fastness in times of danger.

游击队员的山中据点从未被侵略军攻破。

The mountain ___fastness of the guerrilla fighters had never been breached by the invading army.

洪水期间，山顶农舍成了村民寻求高地的避难堡垒。

During the floods, the hilltop farmhouse became a ___fastness for the villagers seeking higher ground.