One day
Start early at the Sagrada Família on a booked slot, then walk or hop the metro down Passeig de Gràcia through the Eixample to see Casa Batlló and La Pedrera from the street. Carry on into the Barri Gòtic for the cathedral and the old lanes, breaking for tapas, then follow La Rambla down past La Boqueria to the harbour and the Columbus monument. Finish with a walk along the water to Barceloneta as the light drops.

