Gorgeous apartment in a central, extremely walkable location (note that Google Maps still routes you to the nearest metro station, Gran Via, although it has been closed for a year). Lots of sirens at night, but also people singing in the streets as they walk home from the bars. We enjoyed falling asleep to the noise of the city.
The apartment is huge and has a very well appointed kitchen, bath, and cushy living room. The door to the washing machine was broken, which rendered it unusable without Javier and Cristine's magic touch, but we had time to wash our laundry by hand and hang dry it, so this was only a minor inconvenience. FYI the bed is quite soft--could be an issue if you have back problems.
Javier and Cristine were extraordinarily welcoming, communicative, and accommodating despite several changes to our itinerary. Thank you for making our accommodations in Madrid a no-brainer so we could focus on enjoying the city!