壁垒森严 heavily fortified
Explanation
形容防御工事坚固，戒备森严。也比喻各方面界限分明，不易逾越。
Describes strong defenses and strict vigilance. It can also describe the sharp separation between different areas.
Origin Story
话说古代有一座名城，地势险要，易守难攻。城墙高耸入云，护城河宽阔深邃，城门更是森严壁垒，层层设防。城内军士训练有素，日夜巡逻，戒备森严。即使是飞鸟，也难以飞越城墙，进入城内。远处的敌军，看到这番景象，只能望城兴叹，无计可施。这座城池，凭借着其壁垒森严的防御体系，以及军民同心的顽强意志，成功地抵御了无数次敌军的进攻，成为了一座坚不可摧的堡垒。后来，“壁垒森严”便用来形容防御体系坚固，戒备森严的状态，也比喻各方面界限分明，不易逾越。
It is said that in ancient times there was a famous city with a strategic location, easy to defend but difficult to attack. The city walls towered into the clouds, the moat was wide and deep, and the gates were heavily fortified with multiple layers of defense. The soldiers in the city were well-trained and patrolled day and night, ready for any attack. Even birds could hardly fly over the walls and enter the city. The enemy troops in the distance could only sigh at the sight of the city, unable to do anything. This city, thanks to its heavily fortified defense system and the unwavering determination of its people, successfully resisted countless attacks by enemy troops and became an impregnable fortress. Later, “壁垒森严” was used to describe the state of strong defense and strict vigilance, and also as a metaphor for clearly defined boundaries that are difficult to cross.
Usage
常用来形容防御工事坚固，戒备森严，或比喻各方面界限分明，不易逾越。
Often used to describe strong defenses and strict vigilance, or as a metaphor for clearly defined boundaries that are difficult to cross.
Examples
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这座城堡壁垒森严，易守难攻。
zhè zuò chéngbǎo bì lěi sēn yán, yì shǒu nán gōng
This castle is heavily fortified and difficult to attack.
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他们之间壁垒森严，很少交流。
tāmen zhī jiān bì lěi sēn yán, hěn shǎo jiāoliú
There is a clear division between them, they rarely communicate with each other.