What makes Spain one of the most popular European countries are its lovely beaches, historical sites and amazing festivals. Tourism is also one of the major industries in Spain, and accounts for almost 11% of its annual GDP. The most popular cities are Madrid, Barcelona and Seville (all of them home to several UNESCO World Heritage Sites). There is the Gugenheim Museum, which draws millions of visitors every year and is a landmark in the history of museum architecture. Spain is also home to the most beautiful islands in Europe that make for a dreamy vacation.