Cristinas place was great. It was in the perfect location in walking distance from all the sights. Basically next door to the Sofia gallery and down the road from the Prado. A great little neighborhood with lots of bars very close and a supermarket at the end of the road. Cristina was not there whilst we stayed, but her neighbor let us in. She did not speak any english, so a bit got lost in translation hehe, but it was not a problem. It was a small but clean room with a couple of very small windows, perfect for a few days. The loungeroom is nice with a small balcony to watch the locals out and about.
I would recommend this to anybody and would stay again if i was in Madrid.