It is a nonrestrictive relative clause because it begins with a relative pronoun, has both a subject and a verb, and is not necessary to the meaning of the sentence.
Explanation:
A non-restrictive relative clause is represented by a sentence that shows additional statements to another sentence. We can say that the bold part shown in the above question is a non-restrictive relative clause because this sentence gives additional information to the reader to understand why Alma wants to visit London and Paris. In addition, this sentence begins with a relative pronoun, has a subject and a verb, and is not necessary for the meaning of the sentence, but presents additional information.
