Minecraft wiki entry for Basic_Fountain_CSG, associated text: Design D is a more complex construction, which begins with an 8×5 wall with a 4×4 pool at the base. It uses a total of 80 blocks, 4 buckets of water, and 2 buckets of lava. The obsidian is optional, but using obsidian instead of other blocks helps prevent accidentally mining through the back wall. Place the water after building, and the lava last of all. (For the adventurous, a fair bit of the back wall could be removed after building the other blocks off it.) The building and use of this design is demonstrated in this video. The finished design will produce two blocks of cobblestone at a time, and when mined, those will fall into the water and be washed towards the player.