平坦的

The rim is flat and there is a rather deep well, or cavetto.

边缘是，有一个相当深底部，或称为圆底。

Various vehicles bowl along over the smooth highway.

各种车辆在高速公路上疾驶。

The river slows on the flat bottom.

河水在河床上减慢流速。

Heading away from the mountains, I soon found an easier path leading downhill to the village.

我背着山走不久, 就发现一条通往该村比较下山小路。