Alejandro's place is a good base from which to explore Madrid. We loved the fact that it is very central and located in the hype neighbourhood of Lavapies. The flat was very clean and is functional, which makes it usable by a couple even though it is very small. He recently installed air conditioning, which is a life safer in the Spanish summer. The only real problem is that the ceiling is low and uneven, so it might be a bit uncomfortable for tall people (I'm 1.85m tall and kept bumping my head against it) - but the listing description is honest and straightforward about that.
I would recomment it to other travellers visiting Madrid.