Parc Esportiu de Cornellà
The outdoor pool at Parc de Llobregat (Av. del Baix Llobregat, s/n) is in Cornellà (which you can get to via L5 on the Metro), but it's more than worth the journey. Designed by Portuguese architect Alvaro Siza, it's quite the gem. The pool has an oval shape and is surrounded by a grassy area where you can play games or just lie back and sunbathe. For a more serious swim, there's also another, covered, pool connected to the outdoor pool by their shared water. Modern, practical, with a play area as well as swimming lanes, this pool is just what the summer ordered.