What a great place to stay while visiting Madrid. Ignacio's apartment is central(we walked everywhere), very clean and has all the amenities you'd need. Having an air conditioner was a blessing with 36 degrees outside temperature.
Be aware of the 6 flight of stairs, but at the same time it's an exercise that can justify all the tapas that you'd eat!
Also because of being on the 6th floor, the apartment gets very little noise from the street, so you can have a good night's sleep.