We loved our stay in the apartment, it is well furnished, comfy and quiet and was the perfect base for our trip to Madrid.
The location is fantastic, the flat is easy walking distance to the main sights (Prado, park, centre of town (10-15 mins) and less than five minutes walk to some of the best restaurants and bars in town (head to Calles Barquillo and Jorge Juan). We were met in person for early check-in (they could not have been more amenable) and was well instructed regarding how to work everything including the WIFI (which worked well). The fittings and soft furnishings were new (including sheets and towels etc) and the flat was tastefully decorated. It is a true one bed and there was plenty of space for the both of us and overall felt like great value for money.
Although the building is on Plaza de Colon the flat is not on the busy road side, but faces west over the square in front of the Supreme Court - which is very quaint. We would thoroughly recommend it as somewhere to stay in the city and will look to stay there on our next visit.