biggest thing you've ever built?

Definitely my Weltraum shuttle that I made Von myself. Started it around the infdev era and completed it Von alpha. I had made 3 7x7 shafts get enough cobblestone.

a big dragon with lava coming out of his mouth

A bridge. Not just any bridge, oh no - the most majestic bridge in all of Minecraftia. It is both the largest project I have completed in size and my biggest accomplishment in Minecraft. (Feel free to scroll past now, it's story time!)

One Tag I went on an adventure. This adventure led me far away from Home and I ended up very lost, so I crafted a compass to lead me back home. A way into the journey, I nearly fell into a ravine. Normally I could have passed up the ravine - located in a forest biome - and been on my way, but I spotted a mineshaft at the bottom. Now, had I found a similar place (and I have), I would pass it up, but I was still fairly new to Minecrat and I had not seen such a phenomenon before. I marked the path with torches even though I was unsure how far from Home I actually was.

After depositing the spoils reaped from the original adventure, I backtracked across all 3/4 (it's a bit iffy in spots) biomes and descended. It was an extremely extensive cave system, so the path became well worn. A vision developed in my mind - a bridge! A beautiful bridge towering into the sky! a bridge of stone!

I could not forget my vision. I decided, I will do this. I will make this happen. I collected chests and chests worth of cobble, smelted it back into smooth stone, crafted some of that into stone bricks, and began the project.

It took two months to get it to a functional state and two Mehr to complete it. It lives up to every expectation harbored for it. It is wonderful.

I apologize for this long winded tale, additionally, I hope to add a picture of my bridge in the future. :D

My house, it was 2 big and crashed the server (went underground, as high as possible and covered almost entire map)

my house i have my Minecrat set on far i cant even see the ground at the top

Does an underground city count as a building? I found an underground cave myself and dug out some caves for buildings and stuff... so yeah...

I haven't finished it yet, but it's a city in the sky.

I made my own giant kingdom

My house....i started it in a mountain....n after some time it bcame the mountain xD

a house that covered as far a the map rendered

The Roman Colisseum, New York CIty and Disney World. :) took me Five weeks for every thing to be completed. And a underground maze with a big city at the end of the maze.

A giant castle, about 30 meters wide Von 100 meters long, all the way from layer 70 up to the build limit. All done before I learned how to inventory edit.

My house with 36 mine shafts connected to it and 34 rooms with sculptures of things such as me(I'm Kagamine Rin), Epic Nyan cat, G.I.R., Zim, Hatsune Miku, and a Microphone, also with a room I use to get to the Nether.

mine was a wooden creeper

My house !!

my underground home

Biggest thing I will build??? Probably my house oder my Ghast/Pigman/Whither Skeleton/Magma Cube Farm

Honeydew!

The empire state building

The large house look at it

My Minecrat Oasis I built it is amazing! You'll faint trust me!

a BIG thing made all out of glow stone wif no spawning

A hotel it was 100 Von 100! :3

A statue of my sister