Here's a super easy way of making a 3D topographical map of anywhere in the world: you could literally be laser-cutting a map within 10 minutes of reading this instructable. I've always liked maps like these and there are some great tutorials out there... but the complexity had always put me off. But I recently learned how to use 123D Make, a free program that slices up STL files into pieces that you can stack together and make a 3D model. So I figured all that I needed was a utility that converted terrain into an STL, and happily, there exists one in Terrain2STL.
Go to the wonderful Terrain2STL utility. You will be greeted by an interactive Google map. Navigate to the geographical area of interest by zooming and dragging, and click "Center To View". Go next to Model Details, and use the Box Size slider to make the red box large enough to incorporate the feature you want. Be aware however that the larger the feature you select, the bigger the STL file you will end up downloading. To start with, I suggest you pick a box size of 1080 or smaller. Under Water and Base Settings, set the Water Drop to 2 mm (to ensure that the shore is clearly demarcated) and the Base Height to the minimum 2 mm. You're ready to make your STL file! Click Create and Download.