Marina's place is very relaxing. It is in a quiet neighborhood with access to many places within walking distance - San Pau (you must see this place), La Sagrada Familia (excellent), and others. Meanwhile, a short cab ride brings you to Las Ramblas and Palau de la Musica (a walk in the Gothico is a must).
Marina provides plenty of towels and other amenities for you. The rooftop area is beautiful and the washer is an added plus with many drying lines for all your stuff.
It is a must stay place for your trip to Barcelona.