Curiosity - What's inside the cube?

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This is a game on iOS and Android, where you chip away at a giant cube with thousands layers cooperatively with the world to find out what's inside. So, what do you think is inside? Somewhere in the game it states that whoever gets to the middle (it can only be one person) will be taken to an online video that will reveal what's inside, so I think that rules out any cash prize or something.