Carmen's apartment is conveniently located near Nervion metro station which is 3 stops from Puerta Jerez, the station nearest to the Cathedral. Carmen and her daughter Lucia are both very friendly and helpful. The apartment was clean and the building had an elevator. The room is located above a sports bar which can get a bit noisy at night, so I recommend bringing ear plugs. The food at the sports bar, however, is very tasty and inexpensive and the staff are quite amicable. So all in all, I would recommend staying at Carmen's place.