On our recent trip to Barcelona we spent an afternoon at Fundació Joan Miró. This is located up in Parc de Montjuïc. We took the Hop On Hop Off bus tour and stopped at the Museum. But you can also take public transportation to get there. We really enjoyed wandering around and looking at all of the art. They also have special exhibitions to check out. Afterwards, we sat and had a snack in the cafe before heading back down the mountain. This Museum wasn't very busy, which makes the experience that much more enjoyable. We highly recommend visiting the Funació Joan Miró on your next visit to Barcelona.
For more information check out their site: https://www.fmirobcn.org/en/