We just wandered the streets!
The Gothic cathedral is fabulous, but you’ve to book well ahead to get into Gaudi’s masterpiece Sagrada Familia!
Lovely beach, marina, harbour with boats offering tours out to sea, lots of restaurants, streets with designer shops and Gaudi architecture. Las Ramblas - a pedestrian street that everyone wants to walk through, so very busy. There’s a zoo and aquarium if you fancy either. My companion had mobility problems, so we didn’t plan much ahead and stopped regularly for outdoor coffee/wine and people watched! We loved Barcelona, but they’ve stopped direct flights from Newcastle, so we’ve just been to Malaga instead.