Multiplayer, First person Sandbox Game for Building Worlds?
In a conversation I recently had with Xuis, he asked me what I would do with a 5x5x5 mile cube, if I could instantaneously design, build, and create anything in it. This tickled my imagination, and soon I started messing with paint sketches and dreaming of the crazy architecture and waterfalls and islands I could build. Think of it as a a simulator for Inception's Limbo, if you will.
So, my question: are there any games that get close to this? GMod has a lot of tools for building stuff, but is useless for landscapes and larger things. Minecraft is pretty close to what I'm dreaming of, but I would love for it to be realistic and beautiful, rather than giant blocks.
And if there isn't anything like this, why not?