Not so much a "build" as a huge Laurasian Nether territory claim with useful resources -- even if in some cases the "resources" are as simple as open area suitable for fighting ghasts and magma slimes, or an awesome lavafall view. There was even a fortress no one had touched before (and, north of the area I care about, a different fortress someone else seemed to have been using). This is the big Nether thing I've been glomping on so hard in recent months.
This basically consists of two subregions. The "Nether park" stretches from x3258 to x3385, and z-499 to z-594. The fortress stretches from x3363 to x3575, and z-503 to z-694. If the northwest "corner" left out of those two regions were also protected that would preserve a lovely ocean view, but I have my doubts that's actually a realistic ask when this claim is already so big...
(Also, feel free to visit. It's as gorgeous as old-school Nether gets!)
EDIT: To clarify one thing, I do want mobs in these areas. Some of the attraction of Meltnomah Park is the opportunity to have a fair fight against ghasts, and Final Fortress being a fortress, there are blaze spawners and other such things.