This hidden base entrance is nearly impossible to find. Simply right click while holding a tool under the location of the obsidian, and poof hidden door appears, to enter simply spam right click and walk into the wall, you'll enter eventually.The obsidian is there because otherwise the wall would be 12 blocks high, and it lets you know where the entrance is. This works because of ghost blocks, and dont worry, the machine is alwalys running, and so if someone joins, (the ghost blocks wouldn't be there), it makes more imediantly! I'm guessing someone else already had this idea, but now its updated for 1.8! I guess. Ignore the rest of this message.