Obsidian roof

The Obsidian roof is a large platform of obsidian above the spawn region of the Overworld.

First Attempt
The first attempt at making an obsidian roof at spawn was done by the group Obsidian Sky. Their reason for doing this was that it will make spawn more difficult by having newfags spawn under the roof, making it dark and harder to see for vanilla players (these reasons are shared by all the other attempts). Eventually the group got bored, only doing 500 x 500 of the spawn region instead of a larger radius.

Second Attempt
The second attempt at this project was done by a group called "Project Obsidian roof" founded by c0mmie_. Not only did they want to make an obsidian roof, they also planned to sponge out all water within the roof and on the edges, and create a large trench filled with lava and withers. Unfortunately, c0mmie's main obsidian and ender-chest dupe stash was griefed 2 weeks after the group was founded, and the discord server slowly became more inactive after that.

Final and successful attempt
The latest attempt to create an obsidian roof over spawn was started by the Infinity Incursion. Using a recently added module in Salhack "autobuild" which allowed semi-automatic platform building, they got to work, and within a few weeks, the roof was created.