Anyone interested in the topic should also check out 2b2t, which is one of the oldest Minecraft anarchy multiplayer servers. It's filled with history and ruins.
I wonder if my base still stands. But the 2b2t server has gone pay 2 play so haven't played for some years. Have the coordinates written down somewhere. Btw it would be really fun with a Minecraft like game focusing on PvP, since Minecraft is focused on co-op it does not have any cheat preventions, which ruins the experience on servers like 2b2t.
