Do not let you mislead from the messy downstairs entrance. Pablo's apartment is small but modern, nice and clean, and has everything anybody might need. The pictures are definitely accurate.
The bedroom has a nice and cozy queen size bed; the living room features a nice and comfortable sofa, which can accommodate another person. The kitchen has also a washing machine. I would definitely recommend it for single or couples. It is in a very busy and central location. However, as the windows are facing an internal courtyard, it is also very quiet. Everything in the center of Madrid can be reached on foot extremely easily (Puerta del Sol, which is the heart of Madrid, is only a 5 minute walk) and there are three very close subway stations in case you don't feel like walking. Pablo is very nice and efficient, and super responsive. I would definitely recommend staying at his apartment.