It's not high mountains and deep valleys that best serve to defend a country.

固国不以山溪之险。

《新英汉大辞典》

For twelve hundred miles the Great Wall ran over high mountains and deep valleys.

这座长城翻高山，越低谷，长达一千二百英里。

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For twelve hundred miles the Great Wall ran over high mountains and deep valleys.

这座长城翻高山，越低谷，长达一千二百英里。

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