We spent 7 nights at Belen's lovely apartment. It is as pictured, very spacious, beautiful and clean. It's very well located and we enjoyed very much exploring the area. There are lots of cafes and restaurants around but the apartment itself is in a quiet side street. From Sol you can get good public transport if you need to - we went to Segovia and Toledo for day trips and Sol was very convenient to get to the train stations for these towns. Communication before and during our stay was great, too, Belen was very helpful. Her nephew Carlos met us at the apartment and checking in was nice and smooth. There is a lift (a very narrow one) which worked only 2 days during the week we spent there. You should note that it could be a bit too hot to sleep comfortably in the bedrooms in summer as the air conditioning has to be turned off at tonight.
The only unpleasant experience we had was with the neighbours above who made a lot of noise till very late at night and then started again early in the morning. The noise insulation is not very good, so when someone walks around in the flat above, you hear every stomping step. So unfortunately we could sleep only from 1-2am till about 8-8.30am and were often woken during the night as well. Belen kindly contacted the neighbours but things didn't improve for us during our stay.