the foot of a mountain，mountain foot，piedmont ；

[例句] 帕萨迪纳坐落于圣加布里埃尔山麓的丘陵地带。 Pasadena lies in the foothills of the San Gabriel mountains.

[例句] 喜马拉雅山脉山麓丘陵 the foothills of the Himalayas