Navbar item that opens image

[iBaker]

I was wanting to look at having an image with hotspot links on it as a site navigation system that drops down from a navbar button so I would like to hear any ideas that anyone may have on how to achieve this.

I was hoping to have on the navbar a button that says "Site Navigation". When a user mouses over the button an image drops down (opens up). The image has hot spots on it so that when a user clicks on one, the image closes up and they are taken to that part of the site.

I know it sounds strange but I think it will suit a site I am working on however I have no idea how I could do it or where I would go to find a script etc that would do the job so any help is greatly appreciated - thanks!