Haha! It’s finished – the version of the grand staircase from the first two Potter films! Join me for a complete video tour!
To get us to this state of completion, I had to add the remaining doorways on the landings:

Then came the big window at the back. Much of the molding is taken directly from that Oxford design I created in the last post. The scene beyond the window is a bit of a cheat…I just did a nighttime render of part of the main castle model, blurred it, and dropped it in like a scenic backdrop in a real set or miniature. It’s not perfect but it gets the job done.

With these elements in place, the only thing remaining was the paintings…but I decided they’d be too much work, I’m omitting them, at least for the time being. They don’t have anything to do with my main purpose (understanding the geometry of the stairs) or my secondary purpose (examining the scale of the space).
Speaking of which, here’s the long-awaited scale comparison between the castle exterior and the grand staircase interior!
They kinda almost fit together at the intended in-universe scale! Of course, if you include all the digital extensions at the top or the extra miniature passes used to extend the bottom, that all goes out the (beautifully mullioned) window. But I think that’s kinda okay.
This concludes my work on this side project…it’s been a fun one! Now back to the main castle model.