My wife and I stayed with Bielka over the 2021 Christmas and New Year Holidays and had a wonderful time. The apartment was very clean, comfortable, warm (even in the winter) and in the best location to see the more local part of Madrid Centro. It was about 5-10 minute walk to El mercado de San Miguel where we bought some delicious tapas, about 30 seconds from El museo de San Isidro which we were able to tour for free, and about 25 minutes to El Parque de Retiro and the Prado museum. There are also a number of grocery stores nearby (Carrefour, Lidl, etc.) in case you need supplies, and the closest metro stop is La Latina which is only about a 3-5 minute walk. This definitely made getting to and from the airport very easy.
Bielka is very friendly and helpful, and gave us some great tips on places to eat when we first arrived. Check in and out was easy, and everything described in her Airbnb listing was as advertised; including the clothes washing machine which worked great! We really enjoyed staying at Bielka's apartment and will definitely stay with her again during our next trip to Spain. Highly recommend!