Hi Ben and Gianluca - I put in a couple of options that will draw an empty graph with bold axes and a visible 20 x 20 grid.
Graphics[GridLines -> {Range[-10, 10], Range[-10, 10]},
Axes -> True, AxesStyle -> Thick, PlotRange -> 10]
![empty graph with axes](http://community.wolfram.com//c/portal/getImageAttachment?filename=emptygrid.png&userId=947139)
Dan Bach
www.dansmath.com