Summer in Spain means long days, warm evenings, and sold-out attraction slots. If you're travelling in July or August, the order you book tickets matters as much as the dates you pick.
Three sites consistently sell out first: Sagrada Família, Alhambra Nasrid Palaces, and Royal Palace weekend mornings. Everything else is usually available with a few days' notice.
What to book first
Start with Alhambra if Granada is on your trip — palace slots are the tightest inventory in Spain. Pick your palace window before booking flights if you can.
Sagrada Família is next. Weekend morning slots in August go 2–3 weeks ahead. Weekday mornings are easier but still worth booking early.
Royal Palace, Guggenheim, and most other sites have more flexibility, but don't leave them to the night before in peak season.
A booking timeline
4–6 weeks before travel: lock in Alhambra palace slot and Sagrada entry for weekend dates.
2 weeks before: book Royal Palace, Guggenheim, and any remaining timed entries.
Day before: check your emails for QR tickets, screenshot them in case of patchy mobile data at the gate.