I had a lovely time in Madrid and the flat is just the ultimate place for a stay in this city.
The location is very central. I did not take any public transports during my time there. You can walk to the most touristic places of the city up to 20 min.
The flat is very comfortable and even though located in the centre it is very quiet and safety.
Sure I will come again to Madrid and I will be pleased to stay at your place.