On rainy days the question is not just "where shall we go?" but "what is open right now?". That is why every plan in this guide comes with its weekend hours: some only open on Sunday mornings (the libraries or Colorin Coloreado) and others only in the afternoon (Tribu House). The museums, the Aquàrium and CaixaForum are open all day.
A tip to avoid overspending: at the Museu Blau, CosmoCaixa and CaixaForum under-16s get in free, so only the adult pays. And on the first Sunday of every month the Museu Blau is free for everyone.
On rainy days in Barcelona, the BabaMap map shows a 🌧️ Indoor button: one tap leaves only the plans under a roof, almost 200, and combined with "Today", only those still open. Three of the venues in this guide are BabaMap partners; we say so on their card.