Setting up underground farms can be challenging due to the requirement for the creation of mud by adding water to bare soil. While it is possible to make mud using a nearby lake, this isn't always optimal, may be risky, and some maps may not have water. Using this basic guide, an underground farm may be built in any flat area open to the sky.

This looks like a good spot.


To get started, a flat area must be used or created with no obstruction to the sky. Optimally the best choice is to find an existing flat plain within your map and build stairs down a single level. If working around hills, you may wish to use the Build > Terrain > Floor tool to create an area of suitable size with another floor above to provide shade. For simplicity's sake, this guide will show how to build in an existing level area.


After building stairs below, use the Terrain > Mine > Wall tool to plan the area you wish to use.

Here's our new, cozy 9 by 9 nook.

"dig it, oh-oh-oh, dig it.
You got to go dig those holes.
dig it, oh-oh-oh, yeah."
                    — Holes, 2003.[www.imdb.com]

After mining below, you must now build your template of holes which will allow rain to fall through. Pause the game here and use a tool such as Terrain > Remove Floor to temporarily outline your walls from underground.

[TODO: Insert a whitty caption here]


Next, begin a pattern of holes from whatever point suits you following a standard knight's move as in chess; two spaces forward, one space to the right or left. The result is a somewhat diagonal grid like below.

King me!


Lastly, we remove the outline with the Cancel Job command and unpause the game to allow a miner to start on our holes.

Looks pretty holey.

Your next problem is preventing grass from growing below and spoiling the otherwise perfectly suitable dirt. Grass may start growing on any dirt tile which receives sunlight. To stop that, make use of the Terrain > Replace Floor tool, choose Clay or any stone, then mirror the hole pattern from above.

Looks familiar.


Now, simply designate your new underground farm. Since mushrooms won't grow in sunlight or on clay/stone, some tiles are not usable, but this is a small price to pay.

It's jolly.

Now that you've got your farm set up, next time it rains, a few drops will fall through the holes and create mud in adjacent tiles. If you've acquired some mushroom seeds, your farmers will plant them on the new mud tiles. Depending on the size of your farm, a few rains will cover the entire area with mud.

Example after a single rain.


Scale your plot up to any size you want.


Overkill? Maybe.