Apologies if this is elsewhere, a search did not find anything related.
I have just returned from a trip to Paris, and visited the model railway under the Gare de l'Est. It is open on Saturday afternoons between 14.30 and 19.00 and has three layouts, 1 HO gauge, 1 O gauge and one O gauge (metre). I attach some images of the HO and O gauge layouts, I can upload more if anybody is interested.
If anybody is able to visit, you have to access the area by going down the Alsace parking ramp (left hand side of the station), going to the bottom and turning right and going through Porte 9 (Door 9), which is the first door you come to. It was held open by a block of wood when I visited. There seems to be no charge, and it is worth a visit.