My sister and I had a really great time staying at Francesco apartment. It's a moment from the airport on the train and within walking distance to La Sagrada Familia and many other sites! Be sure to check out La Boqueria which is a moment away on the metro and Xuerria- a skip down the main street for super fresh, hot churros!
The apartment itself is perfect for everything you need, compact but complete and Francesco is on hand for anything you need help with too!