Great experience with the hat hostel. We made a reservation for 16 people that they were subsequently not able to accommodate and they took care to find an alternative solutions themselves to keep as all together as planned. I also spend one night there and I found the atmosphere very relaxing and charming. The proximity to plaza mayor is outstanding, the staff is very friendly and the rooftop terrace is a big plus. Wi-fi is free and available really everywhere and many other little extra are coming for free (if you need hair drier or an iron or to borrow a padlock). Definitely a great choice if you are up to book a hostel for a trip in Madrid!