What is the simple subject of sentence The savanna with its waving grasses lie next to desert?

Here's why:

* Subject: The subject of a sentence is the person, place, thing, or idea that the sentence is about.

* Simple Subject: The simple subject is the main word or phrase that identifies the subject.

In this sentence, the sentence is about the savanna. While "with its waving grasses" describes the savanna, it's not the main subject.