Anarchy Server Spawns

The spawn of an anarchy server is usually characterized by intense destruction, endless cobblestone mountains, and a lacking of any useful resources, including trees, food, or even dirt. It is usually the most challenging part of surviving an anarchy server, as it takes many tries to get through. Despite this, it is by no means impossible to get out. The best way to restrict newbies from escaping spawn is to extend the destruction seen at spawn, but other methods have been tried.

Lava Wall
The first thing that comes to mind is the lava wall. If someone builds a giant wall of lava around spawn, no one will be able to get through right? Well, no. First of all, the lava wall doesn't even extend to bedrock most of the time, meaning that all someone has to do is go under the wall. Secondly, even for the ones that do go all the way to bedrock, it is just way to easy to destroy it, meaning that some parts of the wall would have water cast over it, enabling escape.

Obsidian Wall
First of all, to even create the wall requires a massive amount of obsidian. Second of all, breaking obsidian with hands is possible. So all that work can simply be reversed in several minutes.

Flood
Another option is to simply flood the spawn with water. This looks promising until you realize that the players can just swim away from spawn, which is easier than traversing through the cobblestone mountains (and the Jesus hack works in most anarchy servers as well!). Also note that using Elytra in the water is difficult, which would anger the people who like to crystal PvP at spawn.

The Ideal Defense
The best way to prevent anyone is to combine the perfect lava with a layer of obsidian below it. Basically, the lava would extend to bedrock, and there would be obsidian surrounding the lava to prevent anyone from removing the lava. There would still be a way past this, probably by going down to bedrock and then trying to build inside the lava wall.