First of all, this is NOT an entire unit. It is essentially a room within a shared flat. The door locks and the room has its own bathroom, but the entire flat consists of several of these rooms, which are occupied by other travelers. You can hear the others speaking in their rooms and in the hallway.
Unfortunately, we had a very uncomfortable time staying in this Airbnb. My girlfriend and I checked in at 9 PM, to which we found a tiny, freezing cold flat, hair on the bed pillows, a clump of hair on the floor next to the bed, and an awful smell. When we mentioned these points to the host, she responded, "Sorry but I honestly think you don't like the studio and you just want a refund." That is exactly what Patricia wrote, word for word.
Somehow, as I was messaging her at 10 PM, her cleaning lady sent her pics of the pillows without hair on them? The cleaning lady apparently told Patricia that she cleaned the bed and it would be impossible for hairs to be on the pillows. Seems odd considering the fact that we were the only two people in the room staring at long black hair on the bed pillows. Someone was lying and it definitely was not me considering I was the one who removed hairs from the pillows with my own hands...
The horrible smell in the room comes from the fact that there is absolutely NO ventilation for the bathroom, even with the fan on. After a single shower, the entire bathroom and room starts to smell of mold and mildew. Since the bed is next to the bathroom, the pillows and sheets reek of mildew -- this smell of the pillows and sheets kept my girlfriend and I up the entire first night we stayed, as the smell was extremely strong.
The AC/heating is inefficient and borderline useless, as the room remains pretty cold as the heating takes several hours to warm a room of 9 square meters...
Finally, after we complained the first night, the cleaning lady came the next day and replaced the sheets and seemingly swept as well.
Other things to note: there is absolutely no storage for suitcases, the bath/shower is very unsafe to step in and out of, the hot water runs out after three minutes, and there is no soap for the sink.
For the cost of the stay, I would absolutely stay somewhere else. There is a hostel in Chamberí, which is exactly the same price, but is extremely clean, has plenty of storage, a helpful host, and a clean bathroom. Unfortunately, this did not have availability during our stay...