During my stay in Barcelona, I purchased the Articket, which grants access to six of Barcelona's most coveted museums, one being Museo Picasso.
The museum feautures the early apprenticeship works of Pablo Picasso. The works were absolutely astonishing.
If you're ever in Barcelona, definitely give this museum a visit, it's worthwhile and for €30, so is the Articket deal. With that, you can also access the CCCB and MACBA.