Lovely, very clean apartment on a quiet street right around the corner from Sagrada Familia. We loved admiring it each night when we returned to the apartment. It was nice to be in a regular neighborhood and not a tourist center (despite being so close to the Sagrada). Yet, it was an easy 1 block walk to the subway so we could get anywhere very easily. The kitchen is perfect sized (grocery stores and a market nearby), the bathroom, too (plenty of hot water) and the beds are comfortable. We slept well! Though the church bells do start ringing at 9 am. There is one flight of stairs to the apartment for those who might be interested.
One of our favorite restaurants, ZED, is just down the street. Definitely some of the best food we had in Barcelona. Toni recommended going to see Sant Pau, a gorgeous Modernista hospital that did not appear in any guidebooks. It's a quick walk from Sagrada and well worth a visit.
Finally, it is easy to get a covid test to re-enter the US at the CMIP EIXAMPLE testing center 1 block away.