Between Asia and Africa lies a land bridge that is known as the Sinai Peninsula.

Would this be a simple sentence?

No. That sentence has two verbs -- lies and is known.

The independent clause is: A land bridge lies between Asia and Africa.

So this sentence is a complex sentence?

Yes.

Thank you very much.

Yes, the sentence "Between Asia and Africa lies a land bridge that is known as the Sinai Peninsula" is a simple sentence. It consists of a subject ("a land bridge") and a predicate ("lies between Asia and Africa"). The sentence presents a straightforward statement without any additional clauses or modifiers.