Minecraft wiki entry for Door-based_iron_golem_farming, associated text: The design is a 16×16 pit 2 blocks below the base of the doors, with a 2×2 hole in the middle, buildings on each side of the pit, and fencing all around. It doesn't matter how you design the buildings as long as the door arrangement is symmetric from the center of the hole. Each building shown here has at least 5 doors facing the pit. Doors on the edge of the pit should be barred from opening using glass blocks if the doors are against the edge of the pit. If the pit is completely fenced, the doors will be set back a block and need not be barred by glass. Also there are doors on other walls; placement doesn't matter as long as it's all symmetrical; an imaginary line from any door through the central hole should intersect another door an equal distance on the other side of the hole.