A recommended itinerary for a visit to Barcelona could include the following:

Day 1:

• Explore the Gothic Quarter, including the Cathedral of Santa Eulalia and Plaça del Rei

• Visit La Rambla and the Mercat de la Boqueria

• See the works of Antoni Gaudí at Park Güell

Day 2:

• Visit the iconic La Sagrada Familia

• Walk along Passeig de Gracia and see Casa Batlló and La Pedrera

• Enjoy the beaches of Barceloneta

Day 3:

• Visit the Picasso Museum

• Explore the Gothic Quarter further, including the Gothic Church of Santa Maria del Mar

• Take a stroll through El Raval and the Born neighborhood

Day 4:

• Visit the Joan Miro Foundation

• Explore the castle of Montjuic and the National Art Museum of Catalonia

• Enjoy some tapas and local cuisine

Note: This itinerary can be adjusted based on individual interests and time constraints.