Hostel Köln is located in a quiet and central Cologne neighborhood, on a side street between Neumarkt and Rudolfplatz. The main attractions of Cologne and cultural facilities are within easy reach on foot and by public transport (just five minutes to a number of bus and tram lines). I was in town for the Christmas markets and Hostel Köln was a short walk from three of them.
Hostel Köln crosses the boundary between hostel and hotel, depending on time of year. This translates into group housing for university exchange programs in summer, and comfortable business hotel accommodation at a good price during Cologne's big trade fairs.
Spartan but pleasing in decor, the entire building, a former office building, is spotlessly maintained. There are dorm rooms, but I lucked into a spacious family room on the seventh (top) floor. It had a great view and proved an excellent place to work (internet access was consistently good). The buffet breakfast was basic but good, and more than adequate to jump-start the day. There is a large terrasse for warm-weather, and a comfortable lobby with pay-as-you-go coffee, tea or cold bottled drinks.
Best, though, were the friendly staff. They were readily available at all times to take my questions, and provided excellent recommendations for area restaurants. I'll definitely book Hostel Köln when I travel to Cologne again.