The Labyrinth World

The Labyrinth World should only be accessed by a portal. A portal that can't be build, it's like the End Portal. This world is like a huge maze. You shouldn't be able to break the walls. It's like a trial. Random mob spawners should spawn around the maze. At the end of the maze you fight a mini boss. You also can't break the giant door that protects the riches of the boss. Once the boss is defeated, then it'll drop an new item, and the door will break open. You can grab the riches and leave. Once you leave the labyrinth you can always go back. You can now break the walls and mess around with it when you arrive again after defeating the boss. Also you may respawn the boss. So it like the Enderdragon but in a huge maze and without Ender-crystals.  So basically it's an unbreakable maze until the boss is defeated. That's my concept.