In reply to Timmd:
This is so easy to do in GIMP (free) or Photoshop, but a bit of a learning curve. These progs are designed to build up composite images out of stacked layers (foregrounds over backgrounds etc.)
Also, if you were to cut ("snip") the foreground image using a separate tool and want to pass this on to some different program to merge with a background, you will need to store that intermediate foreground image in an image protocol that recognizes transparency ( like PNG or TIFF), not JPG.
That is because image files generally store images as rectangles. Your (wanted) parts of the foreground image of the of the city map will have an irregular (non-rectangular) shape. So you need to mark and pass on as transparent the non-map parts of that foreground image so the background will be able to show through. JPG doesn't allow that.
As I say, best to snip a rectangular section of your map image, and then pass that on to GIMP to "cut out the bits you want with scissors", and stack over your background text/whatever.