The ideal length of your visit to Barcelona depends on your interests and how in-depth you want to explore the city and its attractions. Generally, spending 3-4 days in Barcelona is enough to cover the main sights and get a good feel for the city's vibrant atmosphere. With 3-4 days, you can visit iconic landmarks such as La Sagrada Familia, Park Güell, and Casa Batlló, all designed by the famous architect Antoni Gaudí. You'll also have time to explore the Gothic Quarter, stroll along La Rambla, visit the bustling La Boqueria market, and unwind at Barceloneta Beach. If you have more time, extending your stay to 5-7 days will allow you to delve deeper into Barcelona's art, culture, and history. You can visit more museums, such as the Picasso Museum and the National Art Museum of Catalonia, experience the city's culinary scene through tapas bars and local restaurants, and even take a day trip to nearby attractions like Montserrat or the Dali Theatre-Museum in Figueres. Ultimately, the duration of your visit depends on your personal interests and how much you'd like to see and do while in Barcelona. The city has a wealth of history, culture, and modern attractions, so you can easily create an itinerary that suits your preferences.