Depending on your specific requirements you could do a couple of things:
1) You could place a radMap beneath a diagram with transparent background. This is the easiest approach but with it you won't have the full map functionality.
2) You could try to integrate(place the map in the diagram and handle some events) the RadMap and the RadDiagram so that both controls still have zoom, pan, resize and etc.
I've attached a sample project demonstrating the second approach so could you please examine it and if you have more questions feel free to ask.
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