A few years ago- maybe three or four- when minecraft was still modded via the twitch launcher, I downloaded a mod that basically created premade structures. I'm desperately trying to find it again, and having no luck at all.
Basically, it created different structures like houses, towers, aquatic buildings, etc. There were different levels, and they were all themed around, iirc, different glass and clay colours- one was mostly yellows and I think oranges, one was blues/purples. They were pretty 'modern' in style, and each colour was related to a different kind of style of building. Blue/purple was for the buildings that were water-related, etc.

There were different levels of building, too- each had like a house, a big house, an apartment building, and one unique building per theme/style.

It wasn't prefab, I know that much for sure. I feel like it involved putting down a block that would outline the area, and then feeding it the necessary blocks for it to build with? I may be misremembering that.

I really want to find this mod again, and my googling is bringing up nothing.

EDIT: I literally tried googling what I remembered...and found it. It's Archicraft, guys. I'll leave this up for posterity.