We walked 21k around Luxembourg City in 1 day. (31,308 steps up and down the many hills…thanks Fitbit).
We walked around the city and explored a bit before visiting MUDAM Luxembourg (which was fantastic), the Casemates du Bock (not so great for someone with pretty bad anxiety just now!), and we were very thankful for the Pfaffenthal lift at one point! It is a great city for wandering in. We spent most of our time doing just that.
Hotel Bristol: Okay, the cheapest accommodation available in Luxembourg. Not the cleanest, not the best area. Fine for a couple days.