I’ve long known that this structure would get at least one post to itself. It’s big, and so rich with detail! It’s also a weird throwback for me – the first render I did for this project was of the astronomy tower. Or at least, a simple proof of concept. Funnily enough, I never seem to have shared that render, so here it is in all its glory:

Beautiful, I know. 😉
Anyway, as you may know, the original Hogwarts featured the Defense Against the Dark Arts tower – so named by fans because a pullback in GOF implies that Moody’s office is in there. This structure moved but remained fundamentally unchanged all the way until HBP, at which point it was removed, redesigned, and reincarnated as the taller, fancier astronomy tower, which sits where the Dark Tower sat for years 3–5.
From the beginning, the books describe this tower as the castle’s tallest, located very close to the main entrance. The top has crenellated ramparts and a door to a spiral staircase. That’s about all we get. Since the tower was never featured in the first five films, its location, appearance, and even its existence weren’t established in the film canon. But all that had to change in HBP. The filmmakers needed an iconic tower from which a certain somebody could fall in the film’s climax.
As described in my recent blueprint appreciation post, we have some great elevations, sections, and plans for the final design:

It was thus tempting to just build based on these, but I decided to still assemble other references as usual. I was glad I did, because there are details visible in real life that aren’t in those drawings. I even found a few spots where they added extra windows or whatnot. Another complication is that the tower was created at 1:24 and 1:10 scales, plus (I suspect) an even larger miniature or CG asset for the nighttime shot that ascends past Ron, Lavender, and Draco. (That last version has a different design that I’ll ignore.) And then of course there was the full-scale set. I decided to aim for roughly the amount of detail on the main 1:24 miniature, while still paying attention to the others.
Anyway, I captured part of the process in this time lapse:
Or if you just want to look through some renders, enjoy these!
Still more work to do, but it’s a good start!