A Cobblestone Factory is a system/systems that use the reaction of lava and water to make cobblestone from nothing. This system makes it possible to gain cobblestone without wrecking your landscape. The basic cobblestone factory is a lava source and a water source spaced 10 blocks apart in a channel. The lava and water will react, making cobblestone.
How to Build
There are many ways to build a cobblestone factory, but the most common way is to use a stream of water running to the side and having the lava in a contained channel running along it, making cobblestone.
A Cobblestone Factory can be a simple design involving a single pair of water and lava blocks. However, some designs incorporate pistons, red stone, and repeaters to automate or increase the rate of production. These various contraptions can be as simple as a piston set up to extrude the cobblestone to make way for another block. They can also be complex enough that several generators feed into the same point for processing. Where a player stands and breaks them as fast as they are generated.