The girls were not available when we arrived (we arrived after 23 on a Friday night) but Natascha's mum came to let us in and show all we needed to know - She was lovely, very friendly and helpful. The flat is very well decorated, very clean and really comfortable. It is exactly like on the pictures and there is no bad surprises. We loved it. Plus, the location is perfect, within walking distance to bars and Madrid's most famous sites. The area is a bit noisy at night - it did not disturb us at all though - and feels safe.
We had a great time! Really recommend to stay there!