This is a scam operator.
I arrived at 3pm and the place hadn't been cleaned after the last guest. I called the place and they offered several different non-excuses: "there was a long clean in the morning", "the cleaner called in sick", etc. They told me that the cleaner would arrive in an hour: I waited for an hour, and finally gave up, left my bags and went out. An hour later I got a phone call that the cleaner finally arrived, but I needed to go back and let them into the flat -- the cleaners don't have a key. My first night was totally ruined. Thankfully I only stayed two nights.
The place itself is tiny, offers little privacy and is noisy because of the metro line passing underneath. You're not going to get a good night's sleep.
The ironic thing is that they make you fill out a form that goes into details about all of the different fines and charges they make you pay for various things. For example: you want to use their change of bedding? 20 euros if you ask, 100 euros if you don't.
Of course, I didn't get any money back in spite their total lack of professionalism. Stay away, it's better to pay a little bit more and not suffer the stress this operator causes.