Start your morning with a Catalan coffee and croissant at Forn Baluard near the sea, then wander into the winding streets of the Gothic Quarter to visit the serene Plaça Sant Jaume and the carved portals of the Cathedral of Barcelona (admire the cloister and geese). From there, stroll down to La Boqueria Market to sample fresh jamón and seasonal fruit before catching the metro (L3) toward Gràcia to arrive relaxed at Parc Güell for mid-morning views of the city and Gaudí's mosaics.
After soaking in Parc Güell, take the metro back toward the center and enjoy a leisurely lunch at Café de l'Acadèmia in El Born, then wander to Passeig del Born to browse independent boutiques and modernist facades. Continue with a peaceful stroll along the tree-lined Passeig de Colom, stop for a glass of vermut at Bodega La Puntual, and finish the afternoon exploring the maritime displays and history at the Museu d'Història de Catalunya before an early evening tapas crawl.
As twilight falls, drift toward the waterfront for a seafood-focused dinner at La Paradeta in Barceloneta, where you choose fresh catches that chefs grill to order; afterward, stroll the palm-lined Passeig Marítim to watch the lights shimmer on the Mediterranean. Finish the night with inventive cocktails and live jazz at Harlem Jazz Club in the Raval or a relaxed drink at the rooftop terrace of Hotel 1898, enjoying panoramic views of the city as a gentle end to a full first day.
Begin with a sunrise visit to Sagrada Família to admire the light-filled Nativity facade and book a timed-entry tower climb for panoramic city views; afterwards, stroll along Avinguda Gaudí with a quick café stop at Café Sensi for a cortado and a local pastry. Continue down to the elegant stretch of Passeig de Gràcia to admire the façades of Casa Batlló and Casa Milà (La Pedrera) from the outside, then duck into El Nacional for a mid-morning tasting of Catalan cheeses and vermut before a short metro ride toward the beachfront to tie this modernisme morning to the maritime afternoon ahead.
After your Passeig de Gràcia morning, head down to the waterfront and enjoy a relaxed seaside lunch at Can Solé in La Barceloneta, savoring classic paella and a glass of local white wine while watching fisherman boats. Then rent a city bike near Plaça de la Barceloneta to cycle the promenades toward Port Vell, pause at the sleek Maremàgnum for boutique shopping or a gelato, and finish with a contemplative walk along the breakwater to the modern W Barcelona hotel for sunset views over the Mediterranean.
As night falls, wander up to Plaça de Catalunya and take a short stroll into the elegant El Born neighborhood for small-plate dining at Tickets Bar (reserve ahead) or, for a more relaxed vibe, the timeless vermuteria Bar Mut for seasonal Catalan tapas. After dinner, enjoy a postprandial passeig along the illuminated façades of Passeig de Gràcia, stopping for a nightcap on the rooftop terrace of Hotel Majestic to soak in the city lights and reflect on your Modernisme-filled day.