iPhone MKMapKit Image Overlay

How can an ima开发者_StackOverflowge overlay be applied to a MKMapView? Basically, when you zoom in a specific location, I want an image to appear on top of the map that gives a more detailed view of the location.

I've had a look around and found different types of methods to use. I had a working example for an older SDK using the DrawMapRect function but this no longer seems to work on 4.2.

This is a good place to start... http://developer.apple.com/library/ios/#documentation/MapKit/Reference/MKOverlayView_class/Reference/Reference.html

I was looking for polygon sample code though.

@omniscian: If you have solved it you should post something helpful for others. This page has a high google rank.