As any tourist can hope for, Sergio's flat is located close to La Sagrada Familia. This area became the focal point of our trip, and we're glad to have it so easily accessible. There are also many restaurants near Sergio's home--one of our favorites was "Bread with Coffee," which I recommend visiting three blocks away.
As for the flat itself, it was very clean and spacious--especially the bathroom/shower. The bed was pretty comfortable but could have used fluffier pillows.
One thing I failed to realize when booking Sergio's flat is it doesn't have air conditioning. On most occasions this would be fine, however, during our visit in early July, the weather was extremely hot. Being on the 4th floor (80 stairs up), this forced us to open the balcony doors to get fresh air. Mostly what we got was traffic noise from the street below, which made for some sweaty, unrestful nights.
Overall, I really enjoyed Sergio's apartment. However, use caution when booking during the summer months.