Image dragging question...

All,

After being blown away by the stuff behind Google Maps, I am trying to
find out how some of it was done. The part I'm trying to find out right
now is best explained in the following scenario:

Given a picture (200 x 200) and a div (100 x 100), I want to center the
div over the picture and only show the center 100x100 section of the
picture through the div. Then, when the user clicks and drags, I want
to have the picture move under the unmoving div, thereby allowing the
user to drag around and explore the picture through the div.

Is what I want to do possible? If so, any pointers (or outright
explanations) on how to do this?

- John