The location is really great: in the heart of Madrid, all the main touristic attractions are at walking distance, as metro and railway stations; the surroundings are packed with restaurants and clubs. The apartment is small, rather silent, and not really full of light. The kitchen contained very basic facilities, not all sufficient for a family of four. Furniture and beds are not particularly comfortable. The bathroom is functional and nice.
The check-in procedure was upsetting: details of all guests, including passport numbers and graphic signatures are requested through a web-site in advance, but the details about the check-in procedure has been disclosed only few hours in advance, and they required the availability of a cell phone, charged and connected.
We never met the guests, but we communicated through AirBnB and WhatsApp. When we asked for a second pair of keys, we simply got no answer... and the situation caused significant discomfort, as I was in Madrid for business, while my family, for tourism, we needed the house in completely different times.