The Rambla is the focal point of most trips to Barcelona, from Plaça Catalunya, and moving toward the Port, and don't miss the Boqueria market with all its colors and aromas of Mediterranean life. Other must-sees include the Liceu opera house, Plaça Reial, and Gaudí's masterworks, the Palau Güell and the Sagrada Família church.
The Gothic Quarter is a warren of Roman and medieval alleys. Once the Roman Forum, Plaça Sant Jaume opens up between the municipal and Catalonian government palaces. Across Via Laietana, the Ribera-Born neighborhood is centered on the exquisite Mediterranean Gothic Santa Maria del Mar basilica, a step away from the Picasso Museum. A 15-minute walk east from Santa Maria del Mar is Barceloneta, the traditional fisherman's quarter, with a dozen good seafood restaurants.
El Raval, home of the medieval hospital, one of the city's finest Gothic spaces, is a good morning's hike. Gràcia, and Sarrià are each interesting half-day explorations, while Montjuïc has the Museu Nacional d'Art de Catalunya, the Miró Fundació, and the Mies van der Rohe Pavilion.