In a few words: Disappointing. Disgusting. Your worst nightmare.
We arrived late at night in the city because our train got delayed, and we still could check in past midnight (that's a plus at least). BUT, we had to collect the keys in a box somewhere else. That started triggering our minds with a "horror movie" type of feeling.
When arriving in the apartment building the lights were all shut off and it was completely dark, was not easy to find the light switches to move upstairs (4th floor). Since it was a very old building it also had a gut feeling that something was weird (+ horror movie feeling).
When entering the apartment, most of the lights were not working (bedroom, kitchen, living room...) but we were so tired that we thought "let's give it a chance". We started walking around with our phones' flashlights and it turns out the apartment was hardly ever cleaned. The bedlinens were full of hair and red stains (hope it's not blood), the couch had a bed smell, and not even to mention the toilet (that was disgustingly dirty).
We didn’t have the courage to spend the night there, so we left ASAP. The price was low, so we didn't expect any 5 star hotel... but cleanliness should always be there.