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》

You soar effortlessly over high mountains and deep valleys.

你毫不费劲地飞越高山幽谷。

youdao

No mountains, not days; no deep valleys, I do not know of the thick.

不登高山，不知天之大；不临深谷，不知地之厚也。——荀况。

youdao

This is how she described what she could see from that house on a hill: "The far-off mountains in all their grandeur, and the deep valleys, and widely extended plains, and more than all, that little village below, containing only a very few white houses, but more than those young eyes had ever seen."

VOA: special.2010.06.27

It has high mountains. It has valleys formed by ancient ice that cut deep into the Earth millions of years ago.

VOA: special.2009.01.07

There are 36 domed rocks shoulder to shoulder forming deep valleys and steep-sided gorges.

BBC: Lonely Planet's top 10 in Australia's Northern Territory

The sunny island with high mountains and deep valleys also provides herbs and aromatic plants, fruit trees and vegetables, wheat and barley.

NPR: Crete: Ancient Diet with Modern Message

Kigali unfolds across a series of lush mountain tops and deep valleys, with homes and businesses clinging to nearly every inch of hillside.

WSJ: In Mountainous Rwanda, Cricket Faces an Uphill Fight��and Cows