Grand Gothic revival interior based on the (now demolished) Chateau de Noisy, aka Miranda, which formerly existed in Belgium. I made a model of the exterior previously... https://www.cgtrader.com/3d-models/architectural/other/chateau-de-noisy

I couldn't find many reference images of the building in it's pre-ruinous state, so my reconstruction is somewhat speculative.

This interior is made in five parts, the main section (the entrance hall, the hall behind, and another hall off to the side), the stairway section including some vaulted rooms on the upper storey, and three removable walls to make it easier to see the interior chambers. These components are all included as separate objectd (.obj and .dae files). Materials are also included, some for background features being fairly low res. Most can be substituted for other things, if you want to change the wallpaper or the colour of the ceilings. The materials may need to be added manually. Some of the included textures are from textures.com, and include bump-layers and normal maps. Some are a single image that can sometimes be reused as a bump layer.

Sample scenes rendered in Daz3d.

For the decorated windows it's advisable to use an iray glass shader for the pane and then to apply the relevant texture as a diffuse and glossy layer.

Polygon count is for the main section. The stairway bit is as big again.