Land at the foot of mountains is often referred to as a foothill.

Here are some other terms that might describe land at the foot of mountains:

* Mountain base: This is a more general term that simply refers to the area where the mountain meets the ground.

* Valley floor: If the land at the foot of the mountain is a valley, you could call it the valley floor.

* Piedmont: This term is used to describe a region at the foot of a mountain range, often characterized by rolling hills.

* Lowlands: This is a more general term that refers to any area of land that is lower than the surrounding terrain, including land at the foot of mountains.

The specific term used to describe land at the foot of mountains will depend on the specific geographical features and the context in which you are using it.