The Four Points COlogne is a converted older hotel (not sure from what though) and located right across from the main train station (on the opposite of the cathedral), so very central to the city center with many places in walking distance. The former hotel was not very nice, but the hotel was completely remodelled some time ago before being rebranded, so I expect it to be rather nice now.
If you need any more detailed info, eMail me as I live near Cologne...
Greetings - Dirk