What's the biggest thing you built in Minecraft ? A recreation of Game of Thrones' King's Landing maybe? That's cool, I guess, but Denmark just put it to shame. The Danish Geodata Agency has recreated the entire country in Minecraft at a 1:1 scale. If you have 1 terabyte (1000 gigabyte) of space to store it, you can download Denmark for free. They probably have better internet service providers over there.
The Minecraft version of Denmark consists of about 4000 billion bricks. Simon Kokkendorf, an employee at the Danish Geodata Agency came up with the idea to use at as a teaching tool, and built it its surface area by incorporating the agency's 3D elevation model into the game. Kokkendorf and his colleague Thorbjørn Nielsen then added more details like houses, lakes, rivers, lamp-posts, roads, and railways.
You can download the map at the Danish Geodata Agency's website in sections and start building your own structures in Minecraft-Denmark. You can also tear stuff down, but you can't blow the whole place to smithereens with dynamite. The ability to use that item has been removed. Please don't break Denmark.