The apartment is a perfect location for a stay in Madrid.
Chamberi is a beautiful district with a lot of bars and restaurants, enough supermarkets, 24h mini markets and nice building
To the city center it is just a few metro stops and the metro station is just around the corner.
The apartment is very clean, beautiful furnished and there is everything you need. Wifi connections works just fine, there is a washing mashine, coffee,...
Maria was very helpful, waited for us at the apartment since we were a little bit late. But she had maps and a lot of tips prepared.
I would absolutly stay there again.