Book Alhambra and Science Park planetarium on the same day
Two things on this itinerary sell out: Alhambra timed slots (2 to 3 months ahead in peak season) and the Parque de las Ciencias planetarium shows on weekends and school holidays. Book the Alhambra online the day you fix your travel dates. For the planetarium, you cannot book far ahead from home, but buy your slot at the Science Park entrance desk the moment you arrive — shows fill within an hour of opening on busy days. Do not wait until after you have looked at exhibits.