According to an article in PC Games (August 2014, Ben Griffin, p. 12), two people from the Danish Ministry of the Environment “have recreated Denmark on 1:1 scale” in Minecraft. Although the idea came from observing their children playing the game, the construction required non-child-like automation. “By using standard open-source components, it was possible to break this down into a few thousand lines of code, most of which remaps various geospatial objects into Minecraft blocks…In total it took less than a week to calculate all 6437 files,” they said.
Yes, griefers have come, in tanks, blowing up landmarks, and planting their own country’s flags. But, the creators (Simon Kokkendorff and Thorbjørn Nielsen) point out that the vandals only destroyed “a few hectares.”