Note that this is not a mod -- you can't just copy it into your mods directory and expect it to run. It's a mapgen of sorts, so the entire game has to be compiled with it, in the same way you'd compile Minetest normally. This makes it inconvenient, but faster than lua. At the same time, it's not strictly a mapgen, so don't expect to see it in the main branch of the game any time soon.
If you absolutely refuse to compile, you can try this appimage (for Linux) or this windows binary. For Linux, just make the appimage executable (chmod u+x *.AppImage), then run it (./minet*AppImage). The windows version should work like any other windows program. (See also sfan's windows builds.) Note that I don't have the resources to test binaries exhaustively (I don't have windows at all), so they may not work. If you have problems, first try installing the normal minetest binary for your system, then try my binary.
The mapgen produces some nice wilderness with rivers, roads, and an occasional grid of streets with ruins scattered about. There are undergound passages, dungeon geomorphs, and pyramids to explore. The cave system is based on Fun Caves with a few tweaks. It's not strictly dependent on minetest_game, but it does use some of the game's nodes, such as doors and different types of stone.
There is a chaos dimension, accessible with the Trump of Chaos, full of familiar terrain twisted into bizarre shapes. High above, is a network of glass and steel pods, assembled by unknown entities, that protect samples of a variety of plants and animals.
Using the geomoria-based geomorph system, you can add any sort of ruin or dungeon you can imagine with simple lua code. You can also modify or create new cave biomes as easily as surface biomes. The results will be placed by the C code. See the lua documentation.
For the curious, the Lua versions of Squaresville and Fun Caves took about a full second to generate a "chunk" of terrain on my system. This version averages around 150 ms per chunk, so about six times faster.
I strongly recommend my bad_terrain, booty, inspire, nmobs, status, and xlocate mods with this mapgen, as they handle treasure, terrain properties, etc. However, with a bit of tweaking, you can get other treasure and mob mods to work, or just ignore them.
This is a work in progress.
Original Code: LGPL2
Original Textures: CC-BY-SA and CC0
https://github.com/duane-r/minetest/arc ... sville.zip
Edit: I'm no longer maintaining this.