The apartment is located in my view, in the best part of Madrid if you want to be in the centre.
Everything you probably came to Madrid to see is just five to ten minutes walk. Underground and busses there're two minutes away from the apartment.Plenty of excellent restaurants and night life at a doors step.
The apartment is in the fourth floor so very little noice from the street below, has a new lift, so don't hesitate to bring a big bag with you. Also the guest room is a very good size for a couple. There's plenty of space to unpack and put away your clothes. Wardrobe is big and you'll have plenty of drawers. Two big windows to the street make the room easy to air and you'll have a nice morning light.
Is a very quiet area and very safe.
The bathroom is new and has a wonderful shower, kitchen and seating room are very stylish and confortable.
Belén is a wonderful person that will give you any tips you need for your stay in and around Madrid. She's an artist herself and a traveler. A person to have a nice conversation about anything really.
I can't highly recommend this place. It's a very good choice.