The main idea of the show room for exposition is to form different spaces with walls, that do not close completely. moving through the setting, the visitor is passing through different atmospheres. The idea is to have all the walls white from outside and coloured from inside. I have given you one proposal, but you can do it according to your taste.
The hatch is for the pavement. I thing that in these places, it should be very nice to have tiles as I have attached, to define the spaces that should represent the yard.