Hôpital Notre-Dame à la Rose claims to be the oldest hospital in Europe. The only Wikipedia article is in Dutch for some reason when though the town of Lessines is in Wallonia. Superlatives don't always get you on the list and I think there needs to be more. It is more of a church-like hospital anyway, I often felt that I'm in a church altogether. The windows are beautiful, the architecture is great, from the outside you wouldn't think it is a hospital (a modern hospital is around the corner to compare).

Inside most is a museum with display cases and an art gallery. You get plenty to see and it's worth the money but I highly recommend the audio guide. The only issue with the site I have are the weird opening hours from 14:00-18:30 (last entry at 17:45!) and naturally closed on Mondays.

Pro tip: There is parking inside the alley so try there first before driving up the hill