Thanks to a tip from Exiv96, I visited this morning the big garage of Citroën located at Place de l'Yser in Brussels.
It was built in the 30s, and "updated" in 1958 by dividing in several levels (internal steel & concrete structure added inside the building)
A few photos I took:
https://www.facebook.com/antoine.potten/media_set?set=a.10207295800614089.107374- 1833.1257219791&type=3

The visit did not include the repair areas unfortunately