With help, it turns out. Grazzy used the open source Minecraft map editor WorldPainter, which allows users to sculpt and draw detailed landscapes, to convert a map of Hyrule to stacks of Minecraft ...
Enter Arnis, an open source project from [Louis Erbkamm] that can pull in geographic data from OpenStreetMap and turn it into a highly detailed Minecraft map with just a few keystrokes.