4. Sagrada Familia – Barcelona, Spain
The Sagrada Familia is a monumental basilica in Barcelona that showcases the genius of the renowned architect Antoni Gaudí. This ongoing architectural masterpiece combines Gothic and Art Nouveau styles, and its construction has been a work in progress for over a century. The intricately designed towers, captivating facades, and awe-inspiring interiors make the Sagrada Familia a must-visit attraction for architecture enthusiasts and tourists alike.