Oh nice ^^
My greatest Minecraft structure was a house in the shape of a huge sphere, bottom half made entirely of lapis lazuli and top half made of glass, placed on a smaller sphere made of lapis. It had like 3 stories and an attic of sorts at the top of the sphere and I used the smaller one as a basement where I hid all my chests. Then I built a nice farm close to it, dug a huge moat around it and filled it with water, placed fences on the inner side of it with gates here and there, made pens for animals and even had an area where I planted trees to get wood from since we were in the desert. Not sure I still got screenshots, but I'll check xD