For a basic understanding and to see Barcelona's main attractions, a stay of 3 to 4 days is usually recommended. This gives you enough time to visit iconic sights like the Sagrada Família, Park Güell, Casa Batlló, La Rambla, and the historic Barri Gòtic (Gothic Quarter). Additionally, you can reserve a day or two for relaxation at the beach, since Barcelona is a coastal city. If you plan to explore more of the surrounding area, like the neighboring towns and villages in Catalonia, and delve deeper into the culture and gastronomy, consider staying for 5 to 7 days or even longer.