Cologne is not blessed with Airport Hotels which is a shame as it gets many freight movements during the night. The best location reported appears to be the Leonardo Hotel (ex Holiday Inn). Ask for a high level room facing the front of the hotel and you will get limited views of the airport.
With Flight tracking software most movements will be seen from here.
Room 619 and 621 have views however the best reported room is 620 which looks out on the approach to runways 14L and 14R. There is also an fire escape leading to a large window outside of the room which gives views of the cross runway so with flight tracking nothing will be missed.
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