Two days covers Barcelona's headline sights, but it is a highlights rush, because the city really wants three to split the Gaudi trail, the old town, and the beach properly. In 48 hours you can do the Gaudi essentials on day one (Sagrada Familia, the Passeig de Gracia houses, Park Guell) and the old town on day two (the cathedral, El Born, the Picasso Museum, La Boqueria, La Rambla), squeezing in a short beach or sunset stop if energy holds. What you must cut: Montjuic, the Palau de la Musica, a proper beach afternoon, and any slow lingering, so this is a march. It suits a weekend break, a stopover, or a first taste. The non-negotiables: pre-book Sagrada Familia and Park Guell's timed tickets weeks before you fly, plus Casa Batllo or La Pedrera, or you will not get in at all. Base yourself in the Barri Gotic so the old-town day runs on foot and the Gaudi metro hops are quick. Keep your bags zipped, the old town and metro are pickpocket hotspots.