Here you will find a video detailing the lost Atlantis level from God of War II. This is simultaneously the most awesome and most depressing thing ever. It's awesome because it looks really cool, and it's depressing because we'll never get to play it.
Senior Level Designer on God of War II Jonathan Hawkins was told to develop a level for the game based on Atlantis. From the video above it appears he poured a good chunk of his time and effort into it, and then it was cut. That has got to hurt.
Thankfully, a lot of Hawkins's designs went into the final game and there is an Atlantis level in God of War: Ghost of Sparta, but it still doesn't make you any happier that we missed out on this.
God of War Collection: Lost Atlantis Level Revealed [PlayStation Blog]