Hi Asher,
It's a composit of 3 pictures and some digital alterations here and there. Niagara falls is the obvious one here and it was shot at night back in 2003 or so. The model was shot in the studio sometime back in 2010 and the land on which the model is sitting is a very mundane shot from Lake Mead, Las Vegas, 2007.
When I put together all 3 it looks good in color. But then thought about making it little monochromatic/moon lit kind of mood and there you have the result.
This is not one of a kind. I have created quite a few composit images over the past few years. I might share few of them here if you guys like so.
Thanks,
Abhijit