The reason was a memorial for Jean de Selys-Longchamps if I'm not mistaken.
Yes, that was one reason we learned. However, we spoke a member of RAF 3 Sqn and he told us a fuzzy story of a pilot who served with 3 Sqn flying Hawker Typhoons in 1943, while in the Florennes neighbourhood, who was killed in action.
Your last photo is special. Were you allowed to go on the shelter?
Probably not, but we were not sent off, ahem.
Cheers,
Rob
"Boy, let me tell you what: you can wish in one hand, and sh*t in the other, and see which one fills up first" ('Lucky', by Mule)