How do I uncrop an image?

I'm sure that this is probably the simplest question to answer for most of you, but I'm stumped. When I'm in Aperture and press the 'C' key, the Crop window opens. I then left click and drag the image for a new crop. Now my question: how do I undo these steps and view the image again as if I had never pressed the 'C' key? Even when I click on the 'X' in the crop window, the image gets cropped anyway.