@Undead_Zeratul expanding upon Zedar's Forbidden Wing of the Library into a dungeon maze was one of my favorite projects for the server. The original is fairly small, just one hallway connecting a few rooms to the lobby. Each of the rooms were themed around a different block. The lobby and rooms are completely copied in, and the rooms got a few variants added with newer blocks. There's actually only one room saved as a structure, and all the other variants are created via block replace filters.
I'd like to update it and all the structures to the latest Minecraft version. Some day.