BuildTheEarth.net is part of the BuildTheEarth project, where the goal is to recreate the entire Earth in Minecraft at a 1:1 scale. In other words, one block is roughly one meter in real life, so this is a massive long-term build project with a lot of ground to cover.
Anyone can join and help out, whether you want to build on your own or hop into one of the Build Teams and work with others from the network. The server is set up so players can contribute with a pretty simple building system, and no mods are required, just join with Java Minecraft and get building.
The project is open to all languages, nationalities, and regions, and that shared effort is a big part of what makes it special. If you want to learn more or get involved with the community, this is the place to do it.