It's Melchior's Lyithdonea, 9-10 years in the making by a single person. Only in the past couple of years soliciting help for making interiors and such.
I've been considering trying to contribute to either this or the even more amazing Tamriel Rebuilt project. Lyithdonea, for the time right now, seems more focused on the purely graphical aspect of awe, while TR is putting huge effort into making an expanded Morrowind, integrating the main quest into the mainland and having vanilla-like guilds and factions.
To me, contributing to Lyithdonea just seems a bit more accessible. You can grab a single house, decorate it and make a story. And the guy who made it is a giant in the general morrowind modding scene.
I'm just to slow at doing anything when it comes to Morrowind modding, honestly. I guess it's a plus that the game is so old with a small scene in that regard though, I can take my time.