We had a perfect time in San Sebastián. The apartment is very comfortable, has a great view of the cathedral from the balcony, and lift access. It's a lovely 15 minute walk along the water to the old town where all the best pintxos bars are. If you are there on a Thursday, just around the corner from the apartment is an awesome weekly gourmet pintxos night with €1 sushi, empanadillas, meats, drinks etc and live music.. Theres also a big supermarket right nearby if you feel like buying stuff and cooking (the kitchen is well equipped).
Tanya was super friendly and gave us recommendations of things to do/see while in San Sebastián (she'll suggest the 'funicular' up to the old amusement park - DO IT, the view is spectacular).
Would absolutely stay at this apartment next time we come to SS!