We were travelling to Cologne for the first time and like to stay in apartments when possible. Firstly, not being familiar with Cologne, we didn't realise how far this apartment is from the Altstadt and tourist attractions, situated in an underwhelming residential area. We booked through a hotels site that told us a check in time between 14:00 and 23:00 but when we arrived at the address there was no-one at the building, not even a labelled buzzer at the door to ring. I left my partner waiting out the front of the building whilst I tried to find a payphone to call and eventually got through to the owner. He said that he tried to call my mobile (which had run out of battery as we travelled) but that he couldn't be there until 18:00 (it was then already 3:30) as he was at work. Later, we were told off for not being contactable. After having to call him back and insisting that he let us in, someone finally arrived at the site about 40 minutes later. We were let into a very basic ground floor flat with a dilapidated kitchen which reminded me of a university share house. The unmade bed and wet towels on the floor were still remaining from the last tenants and we had to wait whilst they were changed. There was little in the way of curtains to screen the living area from outside passersby. My credit card had already been charged and I was presented with the receipt when we arrived, despite the booking site's claims to the opposite. We decided to take advantage of the 50%cancellation policy and asked for a refund which was obligingly and promptly applied overnight.
I cannot see that this apartment has any advantages: there are similar hotels (in which we stayed) with basic self catering facilities in Cologne that are better located, better staffed, better furnished and just as inexpensive.