Staying in Carlos and Frank's apartment was a pleasure, they could not have been more welcoming and were always very attentive to our needs. It was lovely and clean and spacious (although there were only two of us staying, might be a little more cosy with 4!). The neighbourhood is really nice, with plenty of bars and restaurants, and really close to supermarkets. Only 10 minute from puerta del sol and the Prado too - it is ideally situated. Highly recommended.