要塞坚固的

例句：

1. 1. The fortress was built to protect the city from invaders.
   这座要塞是为了保护城市免受侵略者侵袭而建造的。
2. 2. The castle is a popular tourist destination.
   这座城堡是热门的旅游目的地。
3. 3. The stronghold of the rebels was captured by the government forces.
   叛军的要塞被政府军占领了。