If you want to tour Sagrada Familia, we recommend booking a tour ASAP. Tickets sell out quickly. It's an amazing work of art with many different focal points.
If you want relaxation, we recommend Aire. Thermal baths of different temperatures, massages, sauna, etc.
The Black Virgin of Montserrat (also called Our Lady of Montserrat and La Moreneta) is located inside of the basilica. It is said that the statue of the Virgin Mary and her infant son have healing powers. The Benedictine Abbey dates back to the 9th century and legend has it that this was once was home to the Holy Grail. John and I took the train here a few years ago and enjoyed the history and views.
John and I love a hop-on hop-off bus tour to see many parts of a city.