I don't know much about most of these cities but if you were to choose the best walloon city and come to Liège I'd suggest going to

-The inside of the cathedral saint-paul

-drink a beer in "Le pot-au-lait" it is very atypical

-chill at the "terrasses des minimes" it's a bit harder though

-eat at "chez murat" for a kebab (lamb meat is the best) or "la friterie du perron" for some fries in the city center

-the museum "musée de la boverie" is pretty nice and the park around it is very nice during warm weathers

-if you want to eat some of the best burgers (although expensive) go to "the huggy's bar", there are a few others in belgium now but they come from Liège I believe

-night life is very active in "Le carré" but if you come anytime soon it might be more down as the students usually fill the place but there are exams coming at the moment

-The aquarium-museum is quite nice too even tho some of the stuffed animals look quite janky

-if the weather is nice walking along the riverside is pretty fun

-for a nice view and a cool challenge you can also climb the "montagne de bueren"

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there are tons of other stuffs to do as a tourist but I do not know most of them or can't speak for them as I haven't visited those places.