What are the best places to visit in Spain?

I am planning to visit Spain next month with my <a href="https://mczellbookwriting.com/our-services/ebook-writing-service">ebook writer</a> friends. But we are confused what are the best places we should have to visit. My relative asked me to visit Bilbao because it is a very nice place in Spain. But we will stay in Spain for about 2 weeks. So, kindly mention the best places in Spain in the comment section.