Obvious and different settlements happened in the west extension of the subway that is located in the stratum of Yangtze River valley flat after the construction of the subway tunneling.

南京地铁西延线位于长江漫滩饱和软粘土地层中，地铁施工完成后隧道结构出现了较大的沉降和差异沉降。

youdao

A broad valley opened up leading to a high, flat plateau of cultivated land.

一个宽阔的山谷展开，通向一片平坦的高原耕地。

《柯林斯英汉双解大词典》

The Suguta Valley floor is relatively flat and stands at an elevation about 300 meters (1, 000 feet) above sea level.

苏加塔谷底部相对平坦，海拔约300米(1000英尺)。

youdao

The town lay on a flat plain at the base of an Allegheny Mountain valley so steep that the hillsides rose straight upward along the Little Connemaugh River.

VOA: standard.2010.04.26

His train was high atop a slender viaduct across a flat valley, and immediately ahead of him was train D3115, moving so slowly that it might as well have been a wall.

NEWYORKER: Boss Rail

At this point you will leave the flat Platte River Valley.

FORBES: How Much Should I Have Saved Toward Retirement?

Surrounded by the Pioneer Mountains, Divide was nestled in a flat-backed valley sprinkled with sagebrush and half-burnt two-by-fours, a reminder of when people actually used to live here.

NPR: Excerpt: 'The Selected Works of T.S. Spivet'