When planning the trip we wanted to take advantage of the fact that Cologne was near the border. Looking at the map we realized that Luxembourg was close and that we had never been there before. It also helped that we had friends living there we would get to visit. So we left Cologne on a mid-day train and enjoyed a beautiful ride along the Rhine river to the south.
We found the small country to be very charming and worthy of a visit. We had dinner with our friends and walked the old town on two different days.