Outerra is a game engine which utilizes maps data to form real time lands, therefore the map is a 1:1 scale of Earth (Jesus!).
The images below are of Middle Earth from LOTR, plugged into the engine on a 1:1 scale, found here: http://forum.outerra.com/index.php?topic=2344.0
However I noticed the emphasis on importing models, etc from the outerra site, so maybe this has potential for Rust? (Not the actual map itself, but the system)?
It’s optimized as well, as Outerra states.
Various features of Outerra: http://www.outerra.com/wgallery.html