This minecraft creation makes it possible to get an infinitely long self-building bridge. To achieve this I used pillars which can forward the walkway to the next pillar.

The gap between the pillars can be up to 7 blocks and each pillar itself is 5 blocks long.
The only downside to this is that when the bridge is building, you can fall through the walkway when it is being pushed and you stand on only one block (which is demonstrated at the end of the video)

Click here for the tutorial.