01 Park Güell
Entry to the monumental zone is capped per half-hour and sells out days ahead from April to October; tickets start at €26. The free part of the park is genuinely worth walking, but the terrace with the mosaic bench everybody photographs is inside the paid zone. Take the bus up and walk down.
02 Casa Batlló & Casa Milà
From €45, and this is the Gaudí interior to pick if you only do one: the light well and the roof terrace are the argument for the ticket. Casa Milà a few blocks up is the calmer visit and the better roof. Both include an audio guide, so a guided upgrade adds context rather than access.
03 Sagrada Família
The one to book first and the one our catalogue covers least well, because most of its tickets are sold direct rather than through partners. If a combined pass is your only option, check that it includes tower access before paying for it — the towers are a separate timed slot and the part people queue for.