Mamen and her daughters were fantastic hosts. Despite our last minute booking, they met us when we arrived at the apartment at 1am (ouch!) and provided us with loads of useful information about the local area. If you're a foodie definitely ask their advice about local restaurants!
The apartment's in a great location - really close to Ruben Dario station. It was wonderfully clean and really well designed - the photos don't do it justice. There are sliding sections so you can create separate rooms or make it more open plan. Plus it was designed by Mamen's brother!
Next time I'm in Madrid I'll definitely be staying here!